diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/ClassName.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/ClassName.cs
similarity index 92%
rename from src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/ClassName.cs
rename to src/Microsoft.AspNetCore.Mvc.Razor.Extensions/ClassName.cs
index 509ef56253..6f8033b8e3 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/ClassName.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/ClassName.cs
@@ -4,9 +4,9 @@
 using System.Globalization;
 using System.Text;
 
-namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal
+namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
 {
-    public static class ClassName
+    internal static class ClassName
     {
         public static string GetClassNameFromPath(string path)
         {
@@ -43,7 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal
                 category == UnicodeCategory.Format; // Cf
         }
 
-        private static string SanitizeClassName(string inputName)
+        public static string SanitizeClassName(string inputName)
         {
             if (!IsIdentifierStart(inputName[0]) && IsIdentifierPart(inputName[0]))
             {
diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcRazorTemplateEngine.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcRazorTemplateEngine.cs
index 983b1a616d..9f61050049 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcRazorTemplateEngine.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcRazorTemplateEngine.cs
@@ -3,7 +3,6 @@
 
 using System.IO;
 using System.Text;
-using Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 
 namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcViewDocumentClassifierPass.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcViewDocumentClassifierPass.cs
index b95bcb5fff..da2b2865e6 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcViewDocumentClassifierPass.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/MvcViewDocumentClassifierPass.cs
@@ -1,7 +1,6 @@
 // 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 Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/NamespaceDirective.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/NamespaceDirective.cs
index 437e8a40f3..7d61804390 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/NamespaceDirective.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/NamespaceDirective.cs
@@ -63,13 +63,14 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 {
                     // Beautify the class name since we're using a hierarchy for namespaces.
                     var @class = visitor.FirstClass;
+                    var prefix = Path.GetFileNameWithoutExtension(codeDocument.Source.FileName);
                     if (@class != null && irDocument.DocumentKind == RazorPageDocumentClassifierPass.RazorPageDocumentKind)
                     {
-                        @class.Name = Path.GetFileNameWithoutExtension(codeDocument.Source.FileName) + "_Page";
+                        @class.Name = ClassName.SanitizeClassName(prefix + "_Page");
                     }
                     else if (@class != null && irDocument.DocumentKind == MvcViewDocumentClassifierPass.MvcViewDocumentKind)
                     {
-                        @class.Name = Path.GetFileNameWithoutExtension(codeDocument.Source.FileName) + "_View";
+                        @class.Name = ClassName.SanitizeClassName(prefix + "_View");
                     }
                 }
 
@@ -125,7 +126,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
             for (var i = 0; i < segments.Length - 1; i++)
             {
                 builder.Append('.');
-                builder.Append(segments[i]);
+                builder.Append(ClassName.SanitizeClassName(segments[i]));
             }
 
             @namespace = builder.ToString();
diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/RazorCodeDocumentExtensions.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorCodeDocumentExtensions.cs
similarity index 88%
rename from src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/RazorCodeDocumentExtensions.cs
rename to src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorCodeDocumentExtensions.cs
index ae7bc27e38..2e6c220bcc 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/Internal/RazorCodeDocumentExtensions.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorCodeDocumentExtensions.cs
@@ -4,9 +4,9 @@
 using System;
 using Microsoft.AspNetCore.Razor.Language;
 
-namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal
+namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
 {
-    public static class RazorCodeDocumentExtensions
+    internal static class RazorCodeDocumentExtensions
     {
         private const string RelativePathKey = "relative-path";
 
diff --git a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorPageDocumentClassifierPass.cs b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorPageDocumentClassifierPass.cs
index cbc277788a..321bc172de 100644
--- a/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorPageDocumentClassifierPass.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Razor.Extensions/RazorPageDocumentClassifierPass.cs
@@ -1,7 +1,6 @@
 // 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 Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
diff --git a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcRazorTemplateEngineTest.cs b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcRazorTemplateEngineTest.cs
index 8bb53ffc89..753ed80f00 100644
--- a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcRazorTemplateEngineTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcRazorTemplateEngineTest.cs
@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 using Moq;
 using Xunit;
diff --git a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcViewDocumentClassifierPassTest.cs b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcViewDocumentClassifierPassTest.cs
index 2e2f8de404..4180601bbd 100644
--- a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcViewDocumentClassifierPassTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/MvcViewDocumentClassifierPassTest.cs
@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.IO;
-using Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 using Xunit;
diff --git a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/NamespaceDirectiveTest.cs b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/NamespaceDirectiveTest.cs
index 69c541b8af..32e329d405 100644
--- a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/NamespaceDirectiveTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/NamespaceDirectiveTest.cs
@@ -196,6 +196,44 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
             Assert.Equal("AddUser_Page", @class.Name);
         }
 
+        // Handles cases where invalid characters appears in filenames. Note that we don't sanitize the part of
+        // the namespace that you put in an import, just the file-based-suffix. Garbage in, garbage out.
+        [Fact]
+        public void Pass_SetsNamespaceAndClassName_SanitizesClassAndNamespace()
+        {
+            // Arrange
+            var document = new DocumentIRNode();
+            var builder = RazorIRBuilder.Create(document);
+
+            builder.Push(new DirectiveIRNode()
+            {
+                Descriptor = NamespaceDirective.Directive,
+                Source = new SourceSpan("/Account/_ViewImports.cshtml", 0, 0, 0, 0),
+            });
+            builder.Add(new DirectiveTokenIRNode() { Content = "WebApplication.Account" });
+            builder.Pop();
+
+            var @namespace = new NamespaceDeclarationIRNode() { Content = "default" };
+            builder.Push(@namespace);
+
+            var @class = new ClassDeclarationIRNode() { Name = "default" };
+            builder.Add(@class);
+
+            document.DocumentKind = RazorPageDocumentClassifierPass.RazorPageDocumentKind;
+
+            var codeDocument = RazorCodeDocument.Create(RazorSourceDocument.Create("ignored", "/Account/Manage-Info/Add+User.cshtml"));
+
+            var pass = new NamespaceDirective.Pass();
+            pass.Engine = RazorEngine.CreateEmpty(b => { });
+
+            // Act
+            pass.Execute(codeDocument, document);
+
+            // Assert
+            Assert.Equal("WebApplication.Account.Manage_Info", @namespace.Content);
+            Assert.Equal("Add_User_Page", @class.Name);
+        }
+
         // This is the case where the source file sets the namespace.
         [Fact]
         public void Pass_SetsNamespaceAndClassName_ComputedFromSource_ForView()
diff --git a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/RazorPageDocumentClassifierPassTest.cs b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/RazorPageDocumentClassifierPassTest.cs
index cfcd7b5ab9..f7a9f1e1b1 100644
--- a/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/RazorPageDocumentClassifierPassTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/RazorPageDocumentClassifierPassTest.cs
@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.IO;
-using Microsoft.AspNetCore.Mvc.Razor.Extensions.Internal;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 using Xunit;