[Fixes #157] ErrorPage middleware doesn't show source code lines of Razor files

src/Microsoft.AspNet.Diagnostics/ErrorPageMiddleware.cs

@@ -11,6 +11,7 @@ using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Builder;
 using Microsoft.AspNet.Diagnostics.Views;
+using Microsoft.AspNet.FileProviders;
 using Microsoft.AspNet.Http;
 using Microsoft.Framework.Internal;
 using Microsoft.Framework.Logging;
@@ -28,6 +29,7 @@ namespace Microsoft.AspNet.Diagnostics
         private readonly ErrorPageOptions _options;
         private static readonly bool IsMono = Type.GetType("Mono.Runtime") != null;
         private readonly ILogger _logger;
+        private readonly IFileProvider _fileProvider;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ErrorPageMiddleware"/> class
@@ -35,11 +37,15 @@ namespace Microsoft.AspNet.Diagnostics
         /// <param name="next"></param>
         /// <param name="options"></param>
         public ErrorPageMiddleware(
-            [NotNull] RequestDelegate next, [NotNull] ErrorPageOptions options, ILoggerFactory loggerFactory)
+            [NotNull] RequestDelegate next,
+            [NotNull] ErrorPageOptions options,
+            ILoggerFactory loggerFactory,
+            IApplicationEnvironment appEnvironment)
         {
             _next = next;
             _options = options;
             _logger = loggerFactory.CreateLogger<ErrorPageMiddleware>();
+            _fileProvider = options.FileProvider ?? new PhysicalFileProvider(appEnvironment.ApplicationBasePath);
         }
 
         /// <summary>
@@ -183,31 +189,102 @@ namespace Microsoft.AspNet.Diagnostics
 
             int lineNumber = line.ToInt32();
 
-            return string.IsNullOrEmpty(file)
+            if (string.IsNullOrEmpty(file))
-                ? LoadFrame(string.IsNullOrEmpty(function) ? line.ToString() : function, string.Empty, 0)
+            {
-                : LoadFrame(function, file, lineNumber);
+                return GetStackFrame(
+                    // Handle stack trace lines like
+                    // "--- End of stack trace from previous location where exception from thrown ---"
+                    string.IsNullOrEmpty(function) ? line.ToString() : function,
+                    file: string.Empty,
+                    lineNumber: 0);
+            }
+            else
+            {
+                return GetStackFrame(function, file, lineNumber);
+            }
         }
 
-        private StackFrame LoadFrame(string function, string file, int lineNumber)
+        // make it internal to enable unit testing
+        internal StackFrame GetStackFrame(string function, string file, int lineNumber)
         {
             var frame = new StackFrame { Function = function, File = file, Line = lineNumber };
+
+            if (string.IsNullOrEmpty(file))
+            {
+                return frame;
+            }
+
+            IEnumerable<string> lines = null;
             if (File.Exists(file))
             {
-                var code = File.ReadLines(file);
+                lines = File.ReadLines(file);
-                ReadFrameContent(frame, code, lineNumber, lineNumber);
             }
+            else
+            {
+                // Handle relative paths and embedded files
+                var fileInfo = _fileProvider.GetFileInfo(file);
+                if (fileInfo.Exists)
+                {
+                    // ReadLines doesn't accept a stream. Use ReadLines as its more efficient
+                    // relative to reading lines via stream reader
+                    if (!string.IsNullOrEmpty(fileInfo.PhysicalPath))
+                    {
+                        lines = File.ReadLines(fileInfo.PhysicalPath);
+                    }
+                    else
+                    {
+                        lines = ReadLines(fileInfo);
+                    }
+                }
+            }
+
+            if (lines != null)
+            {
+                ReadFrameContent(frame, lines, lineNumber, lineNumber);
+            }
+
             return frame;
         }
 
-        private void ReadFrameContent(StackFrame frame,
+        // make it internal to enable unit testing
-                                      IEnumerable<string> code,
+        internal void ReadFrameContent(
-                                      int startLineNumber,
+            StackFrame frame,
-                                      int endLineNumber)
+            IEnumerable<string> allLines,
+            int errorStartLineNumberInFile,
+            int errorEndLineNumberInFile)
         {
-            frame.PreContextLine = Math.Max(startLineNumber - _options.SourceCodeLineCount, 1);
+            // Get the line boundaries in the file to be read and read all these lines at once into an array.
-            frame.PreContextCode = code.Skip(frame.PreContextLine - 1).Take(startLineNumber - frame.PreContextLine).ToArray();
+            var preErrorLineNumberInFile = Math.Max(errorStartLineNumberInFile - _options.SourceCodeLineCount, 1);
-            frame.ContextCode = code.Skip(startLineNumber - 1).Take(1 + Math.Max(0, endLineNumber - startLineNumber));
+            var postErrorLineNumberInFile = errorEndLineNumberInFile + _options.SourceCodeLineCount;
-            frame.PostContextCode = code.Skip(startLineNumber).Take(_options.SourceCodeLineCount).ToArray();
+            var codeBlock = allLines
+                .Skip(preErrorLineNumberInFile - 1)
+                .Take(postErrorLineNumberInFile - preErrorLineNumberInFile + 1)
+                .ToArray();
+
+            var numOfErrorLines = (errorEndLineNumberInFile - errorStartLineNumberInFile) + 1;
+            var errorStartLineNumberInArray = errorStartLineNumberInFile - preErrorLineNumberInFile;
+
+            frame.PreContextLine = preErrorLineNumberInFile;
+            frame.PreContextCode = codeBlock.Take(errorStartLineNumberInArray).ToArray();
+            frame.ContextCode = codeBlock
+                .Skip(errorStartLineNumberInArray)
+                .Take(numOfErrorLines)
+                .ToArray();
+            frame.PostContextCode = codeBlock
+                .Skip(errorStartLineNumberInArray + numOfErrorLines)
+                .ToArray();
+        }
+
+        private static IEnumerable<string> ReadLines(IFileInfo fileInfo)
+        {
+            using (var reader = new StreamReader(fileInfo.CreateReadStream()))
+            {
+                string line;
+                while ((line = reader.ReadLine()) != null)
+                {
+                    yield return line;
+                }
+            }
         }
 
         internal class Chunk

src/Microsoft.AspNet.Diagnostics/ErrorPageOptions.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 
+using Microsoft.AspNet.FileProviders;
+
 namespace Microsoft.AspNet.Diagnostics
 {
     /// <summary>
@@ -23,5 +25,13 @@ namespace Microsoft.AspNet.Diagnostics
         /// source code referenced by the exception stack trace is present on the server.
         /// </summary>
         public int SourceCodeLineCount { get; set; }
+
+        /// <summary>
+        /// Provides files containing source code used to display contextual information of an exception.
+        /// </summary>
+        /// <remarks>
+        /// If <c>null</c> <see cref="ErrorPageMiddleware" /> will use a <see cref="PhysicalFileProvider"/>.
+        /// </remarks>
+        public IFileProvider FileProvider { get; set; }
     }
 }

src/Microsoft.AspNet.Diagnostics/Views/CompilationErrorPage.cs

@@ -143,8 +143,8 @@ using Views
 #line hidden
 
             WriteLiteral("                    <li class=\"frame\"");
-            WriteAttribute("tabindex", Tuple.Create(" tabindex=\"", 1231), Tuple.Create("\"", 1251), 
+            WriteAttribute("tabindex", Tuple.Create(" tabindex=\"", 1246), Tuple.Create("\"", 1266), 
-            Tuple.Create(Tuple.Create("", 1242), Tuple.Create<System.Object, System.Int32>(tabIndex, 1242), false));
+            Tuple.Create(Tuple.Create("", 1257), Tuple.Create<System.Object, System.Int32>(tabIndex, 1257), false));
             WriteLiteral(">\r\n");
 #line 42 "CompilationErrorPage.cshtml"
                         
@@ -193,7 +193,7 @@ using Views
 #line hidden
 
 #line 48 "CompilationErrorPage.cshtml"
-                         if (frame.Line != 0 && frame.ContextCode !=null && frame.ContextCode.Any())
+                         if (frame.Line != 0 && frame.ContextCode.Any())
                         {
 
 #line default
@@ -207,15 +207,15 @@ using Views
 #line hidden
 
 #line 51 "CompilationErrorPage.cshtml"
-                                 if (frame.PreContextCode != null)
+                                 if (frame.PreContextCode.Any())
                                 {
 
 #line default
 #line hidden
 
             WriteLiteral("                                    <ol");
-            WriteAttribute("start", Tuple.Create(" start=\"", 1777), Tuple.Create("\"", 1806), 
+            WriteAttribute("start", Tuple.Create(" start=\"", 1790), Tuple.Create("\"", 1819), 
-            Tuple.Create(Tuple.Create("", 1785), Tuple.Create<System.Object, System.Int32>(frame.PreContextLine, 1785), false));
+            Tuple.Create(Tuple.Create("", 1798), Tuple.Create<System.Object, System.Int32>(frame.PreContextLine, 1798), false));
             WriteLiteral(" class=\"collapsible\">\r\n");
 #line 54 "CompilationErrorPage.cshtml"
                                         
@@ -251,8 +251,8 @@ using Views
 #line hidden
 
             WriteLiteral("                                <ol");
-            WriteAttribute("start", Tuple.Create(" start=\"", 2187), Tuple.Create("\"", 2206), 
+            WriteAttribute("start", Tuple.Create(" start=\"", 2200), Tuple.Create("\"", 2219), 
-            Tuple.Create(Tuple.Create("", 2195), Tuple.Create<System.Object, System.Int32>(frame.Line, 2195), false));
+            Tuple.Create(Tuple.Create("", 2208), Tuple.Create<System.Object, System.Int32>(frame.Line, 2208), false));
             WriteLiteral(" class=\"highlight\">\r\n");
 #line 61 "CompilationErrorPage.cshtml"
                                     
@@ -288,15 +288,15 @@ using Views
 #line hidden
 
 #line 66 "CompilationErrorPage.cshtml"
-                                 if (frame.PostContextCode != null)
+                                 if (frame.PostContextCode.Any())
                                 {
 
 #line default
 #line hidden
 
             WriteLiteral("                                    <ol");
-            WriteAttribute("start", Tuple.Create(" start=\'", 2635), Tuple.Create("\'", 2660), 
+            WriteAttribute("start", Tuple.Create(" start=\'", 2646), Tuple.Create("\'", 2671), 
-            Tuple.Create(Tuple.Create("", 2643), Tuple.Create<System.Object, System.Int32>(frame.Line + 1, 2643), false));
+            Tuple.Create(Tuple.Create("", 2654), Tuple.Create<System.Object, System.Int32>(frame.Line + 1, 2654), false));
             WriteLiteral(" class=\"collapsible\">\r\n");
 #line 69 "CompilationErrorPage.cshtml"
                                         

src/Microsoft.AspNet.Diagnostics/Views/CompilationErrorPage.cshtml

@@ -45,10 +45,10 @@
                             <h3>@frame.ErrorDetails</h3>
                         }
 
-                        @if (frame.Line != 0 && frame.ContextCode !=null && frame.ContextCode.Any())
+                        @if (frame.Line != 0 && frame.ContextCode.Any())
                         {
                             <div class="source">
-                                @if (frame.PreContextCode != null)
+                                @if (frame.PreContextCode.Any())
                                 {
                                     <ol start="@frame.PreContextLine" class="collapsible">
                                         @foreach (var line in frame.PreContextCode)
@@ -63,7 +63,7 @@
                                         <li><span>@line</span></li>
                                     }
                                 </ol>
-                                @if (frame.PostContextCode != null)
+                                @if (frame.PostContextCode.Any())
                                 {
                                     <ol start='@(frame.Line + 1)' class="collapsible">
                                         @foreach (var line in frame.PostContextCode)

src/Microsoft.AspNet.Diagnostics/Views/ErrorPage.cs

@@ -65,8 +65,8 @@ using Views
 #line hidden
 
             WriteLiteral("\r\n<!DOCTYPE html>\r\n<html");
-            WriteAttribute("lang", Tuple.Create(" lang=\"", 518), Tuple.Create("\"", 579), 
+            WriteAttribute("lang", Tuple.Create(" lang=\"", 533), Tuple.Create("\"", 594), 
-            Tuple.Create(Tuple.Create("", 525), Tuple.Create<System.Object, System.Int32>(CultureInfo.CurrentUICulture.TwoLetterISOLanguageName, 525), false));
+            Tuple.Create(Tuple.Create("", 540), Tuple.Create<System.Object, System.Int32>(CultureInfo.CurrentUICulture.TwoLetterISOLanguageName, 540), false));
             WriteLiteral(" xmlns=\"http://www.w3.org/1999/xhtml\">\r\n    <head>\r\n        <meta charset=\"utf-8\"" +
 " />\r\n        <title>");
 #line 26 "ErrorPage.cshtml"
@@ -147,8 +147,8 @@ using Views
 #line default
 #line hidden
             WriteLiteral(" in <code");
-            WriteAttribute("title", Tuple.Create(" title=\"", 1895), Tuple.Create("\"", 1919), 
+            WriteAttribute("title", Tuple.Create(" title=\"", 1910), Tuple.Create("\"", 1934), 
-            Tuple.Create(Tuple.Create("", 1903), Tuple.Create<System.Object, System.Int32>(firstFrame.File, 1903), false));
+            Tuple.Create(Tuple.Create("", 1918), Tuple.Create<System.Object, System.Int32>(firstFrame.File, 1918), false));
             WriteLiteral(">");
 #line 50 "ErrorPage.cshtml"
                                                                            Write(System.IO.Path.GetFileName(firstFrame.File));
@@ -281,8 +281,8 @@ using Views
 #line hidden
 
             WriteLiteral("                            <li class=\"frame\"");
-            WriteAttribute("tabindex", Tuple.Create(" tabindex=\"", 3327), Tuple.Create("\"", 3347), 
+            WriteAttribute("tabindex", Tuple.Create(" tabindex=\"", 3342), Tuple.Create("\"", 3362), 
-            Tuple.Create(Tuple.Create("", 3338), Tuple.Create<System.Object, System.Int32>(tabIndex, 3338), false));
+            Tuple.Create(Tuple.Create("", 3353), Tuple.Create<System.Object, System.Int32>(tabIndex, 3353), false));
             WriteLiteral(">\r\n");
 #line 87 "ErrorPage.cshtml"
                                 
@@ -332,8 +332,8 @@ using Views
 #line default
 #line hidden
             WriteLiteral(" in <code");
-            WriteAttribute("title", Tuple.Create(" title=\"", 3742), Tuple.Create("\"", 3761), 
+            WriteAttribute("title", Tuple.Create(" title=\"", 3757), Tuple.Create("\"", 3776), 
-            Tuple.Create(Tuple.Create("", 3750), Tuple.Create<System.Object, System.Int32>(frame.File, 3750), false));
+            Tuple.Create(Tuple.Create("", 3765), Tuple.Create<System.Object, System.Int32>(frame.File, 3765), false));
             WriteLiteral(">");
 #line 94 "ErrorPage.cshtml"
                                                                                 Write(System.IO.Path.GetFileName(frame.File));
@@ -355,7 +355,7 @@ using Views
 #line hidden
 
 #line 97 "ErrorPage.cshtml"
-                                 if (frame.Line != 0 && frame.ContextCode !=null && frame.ContextCode.Any())
+                                 if (frame.Line != 0 && frame.ContextCode.Any())
                                 {
 
 #line default
@@ -369,15 +369,15 @@ using Views
 #line hidden
 
 #line 100 "ErrorPage.cshtml"
-                                         if (frame.PreContextCode != null)
+                                         if (frame.PreContextCode.Any())
                                         {
 
 #line default
 #line hidden
 
             WriteLiteral("                                            <ol");
-            WriteAttribute("start", Tuple.Create(" start=\"", 4194), Tuple.Create("\"", 4223), 
+            WriteAttribute("start", Tuple.Create(" start=\"", 4207), Tuple.Create("\"", 4236), 
-            Tuple.Create(Tuple.Create("", 4202), Tuple.Create<System.Object, System.Int32>(frame.PreContextLine, 4202), false));
+            Tuple.Create(Tuple.Create("", 4215), Tuple.Create<System.Object, System.Int32>(frame.PreContextLine, 4215), false));
             WriteLiteral(" class=\"collapsible\">\r\n");
 #line 103 "ErrorPage.cshtml"
                                                 
@@ -413,8 +413,8 @@ using Views
 #line hidden
 
             WriteLiteral("\r\n                                        <ol");
-            WriteAttribute("start", Tuple.Create(" start=\"", 4663), Tuple.Create("\"", 4682), 
+            WriteAttribute("start", Tuple.Create(" start=\"", 4676), Tuple.Create("\"", 4695), 
-            Tuple.Create(Tuple.Create("", 4671), Tuple.Create<System.Object, System.Int32>(frame.Line, 4671), false));
+            Tuple.Create(Tuple.Create("", 4684), Tuple.Create<System.Object, System.Int32>(frame.Line, 4684), false));
             WriteLiteral(" class=\"highlight\">\r\n");
 #line 111 "ErrorPage.cshtml"
                                             
@@ -450,15 +450,15 @@ using Views
 #line hidden
 
 #line 117 "ErrorPage.cshtml"
-                                         if (frame.PostContextCode != null)
+                                         if (frame.PostContextCode.Any())
                                         {
 
 #line default
 #line hidden
 
             WriteLiteral("                                            <ol");
-            WriteAttribute("start", Tuple.Create(" start=\'", 5177), Tuple.Create("\'", 5202), 
+            WriteAttribute("start", Tuple.Create(" start=\'", 5188), Tuple.Create("\'", 5213), 
-            Tuple.Create(Tuple.Create("", 5185), Tuple.Create<System.Object, System.Int32>(frame.Line + 1, 5185), false));
+            Tuple.Create(Tuple.Create("", 5196), Tuple.Create<System.Object, System.Int32>(frame.Line + 1, 5196), false));
             WriteLiteral(" class=\"collapsible\">\r\n");
 #line 120 "ErrorPage.cshtml"
                                                 

src/Microsoft.AspNet.Diagnostics/Views/ErrorPage.cshtml

@@ -94,10 +94,10 @@
                                     <h3>@frame.Function in <code title="@frame.File">@System.IO.Path.GetFileName(frame.File)</code></h3>
                                 }
 
-                                @if (frame.Line != 0 && frame.ContextCode !=null && frame.ContextCode.Any())
+                                @if (frame.Line != 0 && frame.ContextCode.Any())
                                 {
                                     <div class="source">
-                                        @if (frame.PreContextCode != null)
+                                        @if (frame.PreContextCode.Any())
                                         {
                                             <ol start="@frame.PreContextLine" class="collapsible">
                                                 @foreach (var line in frame.PreContextCode)
@@ -114,7 +114,7 @@
                                             }
                                         </ol>
 
-                                        @if (frame.PostContextCode != null)
+                                        @if (frame.PostContextCode.Any())
                                         {
                                             <ol start='@(frame.Line + 1)' class="collapsible">
                                                 @foreach (var line in frame.PostContextCode)

src/Microsoft.AspNet.Diagnostics/Views/StackFrame.cs

@@ -3,6 +3,7 @@
 
 
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNet.Diagnostics.Views
 {
@@ -32,19 +33,19 @@ namespace Microsoft.AspNet.Diagnostics.Views
         public int PreContextLine { get; set; }
 
         /// <summary>
-        /// 
+        /// Lines of code before the actual error line(s).
         /// </summary>
-        public IEnumerable<string> PreContextCode { get; set; }
+        public IEnumerable<string> PreContextCode { get; set; } = Enumerable.Empty<string>();
 
         /// <summary>
-        /// 
+        /// Line(s) of code responsible for the error.
         /// </summary>
-        public IEnumerable<string> ContextCode { get; set; }
+        public IEnumerable<string> ContextCode { get; set; } = Enumerable.Empty<string>();
 
         /// <summary>
-        /// 
+        /// Lines of code after the actual error line(s).
         /// </summary>
-        public IEnumerable<string> PostContextCode { get; set; }
+        public IEnumerable<string> PostContextCode { get; set; } = Enumerable.Empty<string>();
 
         /// <summary>
         /// Specific error details for this stack frame.

src/Microsoft.AspNet.Diagnostics/project.json

@@ -7,13 +7,17 @@
     },
     "dependencies": {
         "Microsoft.AspNet.Diagnostics.Abstractions": "1.0.0-*",
+        "Microsoft.AspNet.FileProviders.Physical": "1.0.0-*",
         "Microsoft.AspNet.Http.Extensions": "1.0.0-*",
         "Microsoft.AspNet.WebUtilities": "1.0.0-*",
+        "Microsoft.Framework.Logging.Abstractions": "1.0.0-*",
+        "Microsoft.Framework.NotNullAttribute.Sources": {
+            "type": "build",
+            "version": "1.0.0-*"
+        },
         "Microsoft.Framework.OptionsModel": "1.0.0-*",
-        "Microsoft.Framework.NotNullAttribute.Sources": { "type": "build", "version": "1.0.0-*" },
-        "Microsoft.Framework.WebEncoders.Core": "1.0.0-*",
         "Microsoft.Framework.Runtime.Compilation.Abstractions": "1.0.0-*",
-        "Microsoft.Framework.Logging.Abstractions": "1.0.0-*"
+        "Microsoft.Framework.WebEncoders.Core": "1.0.0-*"
     },
     "frameworks": {
         "dnx451": {},

test/Microsoft.AspNet.Diagnostics.Tests/ErrorPageMiddlewareTest.cs

@@ -0,0 +1,451 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.Versioning;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Diagnostics.Views;
+using Microsoft.AspNet.FileProviders;
+using Microsoft.Framework.Caching;
+using Microsoft.Framework.Logging;
+using Microsoft.Framework.Runtime;
+using Xunit;
+
+namespace Microsoft.AspNet.Diagnostics
+{
+    public class ErrorPageMiddlewareTest
+    {
+        [Theory]
+        [InlineData("TestFiles/SourceFile.txt")]
+        [InlineData(@"TestFiles\SourceFile.txt")]
+        public void UsesDefaultFileProvider_IfNotProvidedOnOptions(string relativePath)
+        {
+            // Arrange & Act
+            var middleware = GetErrorPageMiddleware(fileProvider: null);
+            var stackFrame = middleware.GetStackFrame("func1", relativePath, lineNumber: 10);
+
+            // Assert
+            // Lines 4-16 (inclusive) is the code block
+            Assert.Equal(4, stackFrame.PreContextLine);
+            Assert.Equal(GetCodeLines(4, 9), stackFrame.PreContextCode);
+            Assert.Equal(GetCodeLines(10, 10), stackFrame.ContextCode);
+            Assert.Equal(GetCodeLines(11, 16), stackFrame.PostContextCode);
+        }
+
+        public static TheoryData<string> AbsolutePathsData
+        {
+            get
+            {
+                var rootPath = Directory.GetCurrentDirectory();
+                return new TheoryData<string>()
+                {
+                    Path.Combine(rootPath, "TestFiles/SourceFile.txt"),
+                    Path.Combine(rootPath, @"TestFiles\SourceFile.txt")
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(AbsolutePathsData))]
+        public void DisplaysSourceCodeLines_ForAbsolutePaths(string absoluteFilePath)
+        {
+            // Arrange
+            var rootPath = Directory.GetCurrentDirectory();
+            // PhysicalFileProvider handles only relative paths but we fall back to work with absolute paths too
+            var provider = new PhysicalFileProvider(rootPath);
+
+            // Act
+            var middleware = GetErrorPageMiddleware(provider);
+            var stackFrame = middleware.GetStackFrame("func1", absoluteFilePath, lineNumber: 10);
+
+            // Assert
+            // Lines 4-16 (inclusive) is the code block
+            Assert.Equal(4, stackFrame.PreContextLine);
+            Assert.Equal(GetCodeLines(4, 9), stackFrame.PreContextCode);
+            Assert.Equal(GetCodeLines(10, 10), stackFrame.ContextCode);
+            Assert.Equal(GetCodeLines(11, 16), stackFrame.PostContextCode);
+        }
+
+        [Theory]
+        [InlineData("TestFiles/SourceFile.txt")]
+        [InlineData(@"TestFiles\SourceFile.txt")]
+        public void DisplaysSourceCodeLines_ForRelativePaths(string relativePath)
+        {
+            // Arrange
+            var rootPath = Directory.GetCurrentDirectory();
+            var provider = new PhysicalFileProvider(rootPath);
+
+            // Act
+            var middleware = GetErrorPageMiddleware(provider);
+            var stackFrame = middleware.GetStackFrame("func1", relativePath, lineNumber: 10);
+
+            // Assert
+            // Lines 4-16 (inclusive) is the code block
+            Assert.Equal(4, stackFrame.PreContextLine);
+            Assert.Equal(GetCodeLines(4, 9), stackFrame.PreContextCode);
+            Assert.Equal(GetCodeLines(10, 10), stackFrame.ContextCode);
+            Assert.Equal(GetCodeLines(11, 16), stackFrame.PostContextCode);
+        }
+
+        [Theory]
+        [InlineData("TestFiles/EmbeddedSourceFile.txt")]
+        //[InlineData(@"TestFiles\EmbeddedSourceFile.txt")]
+        public void DisplaysSourceCodeLines_ForRelativeEmbeddedPaths(string relativePath)
+        {
+            // Arrange
+            var provider = new EmbeddedFileProvider(
+                GetType().GetTypeInfo().Assembly,
+                baseNamespace: $"{typeof(ErrorPageMiddlewareTest).GetTypeInfo().Assembly.GetName().Name}.Resources");
+
+            // Act
+            var middleware = GetErrorPageMiddleware(provider);
+            var stackFrame = middleware.GetStackFrame("func1", relativePath, lineNumber: 10);
+
+            // Assert
+            // Lines 4-16 (inclusive) is the code block
+            Assert.Equal(4, stackFrame.PreContextLine);
+            Assert.Equal(GetCodeLines(4, 9), stackFrame.PreContextCode);
+            Assert.Equal(GetCodeLines(10, 10), stackFrame.ContextCode);
+            Assert.Equal(GetCodeLines(11, 16), stackFrame.PostContextCode);
+        }
+
+        public static TheoryData<ErrorData> DisplaysSourceCodeLines_PreAndPostErrorLineData
+        {
+            get
+            {
+                return new TheoryData<ErrorData>()
+                {
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 30),
+                        ErrorStartLine = 10,
+                        ErrorEndLine = 10,
+                        ExpectedPreContextLine = 4,
+                        ExpectedPreErrorCode = GetCodeLines(4, 9),
+                        ExpectedErrorCode = GetCodeLines(10, 10),
+                        ExpectedPostErrorCode = GetCodeLines(11, 16)
+                    },
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 30),
+                        ErrorStartLine = 10,
+                        ErrorEndLine = 13, // multi-line error
+                        ExpectedPreContextLine = 4,
+                        ExpectedPreErrorCode = GetCodeLines(4, 9),
+                        ExpectedErrorCode = GetCodeLines(10, 13),
+                        ExpectedPostErrorCode = GetCodeLines(14, 19)
+                    },
+
+                    // PreErrorCode less than source code line count
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 10),
+                        ErrorStartLine = 1,
+                        ErrorEndLine = 1,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = Enumerable.Empty<string>(),
+                        ExpectedErrorCode = GetCodeLines(1, 1),
+                        ExpectedPostErrorCode = GetCodeLines(2, 7)
+                    },
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 10),
+                        ErrorStartLine = 3,
+                        ErrorEndLine = 5,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = GetCodeLines(1, 2),
+                        ExpectedErrorCode = GetCodeLines(3, 5),
+                        ExpectedPostErrorCode = GetCodeLines(6, 10)
+                    },
+
+                    // PostErrorCode less than source code line count
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 10),
+                        ErrorStartLine = 10,
+                        ErrorEndLine = 10,
+                        ExpectedPreContextLine = 4,
+                        ExpectedPreErrorCode = GetCodeLines(4, 9),
+                        ExpectedErrorCode = GetCodeLines(10, 10),
+                        ExpectedPostErrorCode = Enumerable.Empty<string>()
+                    },
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 10),
+                        ErrorStartLine = 7,
+                        ErrorEndLine = 10,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = GetCodeLines(1, 6),
+                        ExpectedErrorCode = GetCodeLines(7, 10),
+                        ExpectedPostErrorCode = Enumerable.Empty<string>()
+                    },
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 10),
+                        ErrorStartLine = 5,
+                        ErrorEndLine = 8,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = GetCodeLines(1, 4),
+                        ExpectedErrorCode = GetCodeLines(5, 8),
+                        ExpectedPostErrorCode = GetCodeLines(9, 10)
+                    },
+
+                    // Pre and Post error code less than source code line count
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 4),
+                        ErrorStartLine = 2,
+                        ErrorEndLine = 3,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = GetCodeLines(1, 1),
+                        ExpectedErrorCode = GetCodeLines(2, 3),
+                        ExpectedPostErrorCode = GetCodeLines(4, 4)
+                    },
+                    new ErrorData()
+                    {
+                        AllLines = GetCodeLines(1, 4),
+                        ErrorStartLine = 1,
+                        ErrorEndLine = 4,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = Enumerable.Empty<string>(),
+                        ExpectedErrorCode = GetCodeLines(1, 4),
+                        ExpectedPostErrorCode = Enumerable.Empty<string>()
+                    },
+
+                    // change source code line count
+                    new ErrorData()
+                    {
+                        SourceCodeLineCount = 1,
+                        AllLines = GetCodeLines(1, 1),
+                        ErrorStartLine = 1,
+                        ErrorEndLine = 1,
+                        ExpectedPreContextLine = 1,
+                        ExpectedPreErrorCode = Enumerable.Empty<string>(),
+                        ExpectedErrorCode = GetCodeLines(1, 1),
+                        ExpectedPostErrorCode = Enumerable.Empty<string>()
+                    },
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(DisplaysSourceCodeLines_PreAndPostErrorLineData))]
+        public void DisplaysSourceCodeLines_PreAndPostErrorLine(ErrorData errorData)
+        {
+            // Arrange
+            var middleware = GetErrorPageMiddleware();
+            var stackFrame = new StackFrame();
+
+            // Act
+            middleware.ReadFrameContent(
+                stackFrame, errorData.AllLines, errorData.ErrorStartLine, errorData.ErrorEndLine);
+
+            // Assert
+            Assert.Equal(errorData.ExpectedPreContextLine, stackFrame.PreContextLine);
+            Assert.Equal(errorData.ExpectedPreErrorCode, stackFrame.PreContextCode);
+            Assert.Equal(errorData.ExpectedErrorCode, stackFrame.ContextCode);
+            Assert.Equal(errorData.ExpectedPostErrorCode, stackFrame.PostContextCode);
+        }
+
+        private static IEnumerable<string> GetCodeLines(int fromLine, int toLine)
+        {
+            var start = fromLine;
+            var count = toLine - fromLine + 1;
+            return Enumerable.Range(start, count).Select(i => string.Format("Line{0}", i));
+        }
+
+        private ErrorPageMiddleware GetErrorPageMiddleware(
+            IFileProvider fileProvider = null, int sourceCodeLineCount = 6)
+        {
+            var errorPageOptions = new ErrorPageOptions();
+            errorPageOptions.SourceCodeLineCount = sourceCodeLineCount;
+
+            if (fileProvider != null)
+            {
+                errorPageOptions.FileProvider = fileProvider;
+            }
+
+            var middleware = new ErrorPageMiddleware(
+                (httpContext) => { return Task.FromResult(0); },
+                errorPageOptions,
+                new LoggerFactory(),
+                new TestApplicationEnvironment());
+
+            return middleware;
+        }
+
+        private class TestApplicationEnvironment : IApplicationEnvironment
+        {
+            public string ApplicationBasePath
+            {
+                get
+                {
+                    return Directory.GetCurrentDirectory();
+                }
+            }
+
+            public string ApplicationName
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public string ApplicationVersion
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public string Configuration
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public FrameworkName RuntimeFramework
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public string Version
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public object GetData(string name)
+            {
+                throw new NotImplementedException();
+            }
+
+            public void SetData(string name, object value)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private class TestFileProvider : IFileProvider
+        {
+            private readonly IEnumerable<string> _sourceCodeLines;
+
+            public TestFileProvider(IEnumerable<string> sourceCodeLines)
+            {
+                _sourceCodeLines = sourceCodeLines;
+            }
+
+            public IDirectoryContents GetDirectoryContents(string subpath)
+            {
+                throw new NotImplementedException();
+            }
+
+            public IFileInfo GetFileInfo(string subpath)
+            {
+                return new TestFileInfo(_sourceCodeLines);
+            }
+
+            public IExpirationTrigger Watch(string filter)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private class TestFileInfo : IFileInfo
+        {
+            private readonly MemoryStream _stream;
+
+            public TestFileInfo(IEnumerable<string> sourceCodeLines)
+            {
+                _stream = new MemoryStream();
+                using (var writer = new StreamWriter(_stream, Encoding.UTF8, 1024, leaveOpen: true))
+                {
+                    foreach (var line in sourceCodeLines)
+                    {
+                        writer.WriteLine(line);
+                    }
+                }
+                _stream.Seek(0, SeekOrigin.Begin);
+            }
+
+            public bool Exists
+            {
+                get
+                {
+                    return true;
+                }
+            }
+
+            public bool IsDirectory
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public DateTimeOffset LastModified
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public long Length
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public string Name
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public string PhysicalPath
+            {
+                get
+                {
+                    return null;
+                }
+            }
+
+            public Stream CreateReadStream()
+            {
+                return _stream;
+            }
+        }
+
+        public class ErrorData
+        {
+            public int SourceCodeLineCount { get; set; } = 6;
+            public IEnumerable<string> AllLines { get; set; }
+            public int ErrorStartLine { get; set; }
+            public int ErrorEndLine { get; set; }
+            public int ExpectedPreContextLine { get; set; }
+            public IEnumerable<string> ExpectedPreErrorCode { get; set; }
+            public IEnumerable<string> ExpectedErrorCode { get; set; }
+            public IEnumerable<string> ExpectedPostErrorCode { get; set; }
+        }
+    }
+}

test/Microsoft.AspNet.Diagnostics.Tests/Resources/TestFiles/EmbeddedSourceFile.txt

@@ -0,0 +1,30 @@
+Line1
+Line2
+Line3
+Line4
+Line5
+Line6
+Line7
+Line8
+Line9
+Line10
+Line11
+Line12
+Line13
+Line14
+Line15
+Line16
+Line17
+Line18
+Line19
+Line20
+Line21
+Line22
+Line23
+Line24
+Line25
+Line26
+Line27
+Line28
+Line29
+Line30

test/Microsoft.AspNet.Diagnostics.Tests/TestFiles/SourceFile.txt

@@ -0,0 +1,30 @@
+Line1
+Line2
+Line3
+Line4
+Line5
+Line6
+Line7
+Line8
+Line9
+Line10
+Line11
+Line12
+Line13
+Line14
+Line15
+Line16
+Line17
+Line18
+Line19
+Line20
+Line21
+Line22
+Line23
+Line24
+Line25
+Line26
+Line27
+Line28
+Line29
+Line30

test/Microsoft.AspNet.Diagnostics.Tests/project.json

@@ -4,6 +4,7 @@
     },
     "dependencies": {
         "Microsoft.AspNet.Diagnostics.Elm": "1.0.0-*",
+        "Microsoft.AspNet.FileProviders.Embedded": "1.0.0-*",
         "Microsoft.AspNet.TestHost": "1.0.0-*",
         "Microsoft.Framework.DependencyInjection": "1.0.0-*",
         "xunit.runner.aspnet": "2.0.0-aspnet-*"
@@ -18,7 +19,10 @@
         "dnxcore50": {
         }
     },
+
     "commands": {
         "test": "xunit.runner.aspnet"
-    }
+    },
+
+    "resource": [ "Resources/**" ]
 }