From cc053ddbbf1ac3ad0584b58f0a70097c4fee3566 Mon Sep 17 00:00:00 2001
From: Steve Sanderson <SteveSandersonMS@users.noreply.github.com>
Date: Tue, 30 Jan 2018 15:31:23 +0000
Subject: [PATCH] Better validation of C# class names in RazorCompiler

---
 .../Core/RazorCompilation/RazorCompiler.cs            | 11 ++++++-----
 .../Microsoft.AspNetCore.Blazor.Build.csproj          |  1 +
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Blazor.Build/Core/RazorCompilation/RazorCompiler.cs b/src/Microsoft.AspNetCore.Blazor.Build/Core/RazorCompilation/RazorCompiler.cs
index 187cdfae6c..bf10a4ef63 100644
--- a/src/Microsoft.AspNetCore.Blazor.Build/Core/RazorCompilation/RazorCompiler.cs
+++ b/src/Microsoft.AspNetCore.Blazor.Build/Core/RazorCompilation/RazorCompiler.cs
@@ -9,7 +9,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Text.RegularExpressions;
+using System.CodeDom.Compiler;
 
 namespace Microsoft.AspNetCore.Blazor.Build.Core.RazorCompilation
 {
@@ -18,9 +18,7 @@ namespace Microsoft.AspNetCore.Blazor.Build.Core.RazorCompilation
     /// </summary>
     public class RazorCompiler
     {
-        // TODO: Relax this to allow for whatever C# allows
-        private static Regex ClassNameRegex
-            = new Regex("^[a-z][a-z0-9_]*$", RegexOptions.IgnoreCase);
+        private static CodeDomProvider _csharpCodeDomProvider = CodeDomProvider.CreateProvider("c#");
 
         /// <summary>
         /// Writes C# source code representing Blazor components defined by Razor files.
@@ -150,12 +148,15 @@ namespace Microsoft.AspNetCore.Blazor.Build.Core.RazorCompilation
 
             // Use the filename as class name
             var inputBasename = Path.GetFileNameWithoutExtension(inputFilePathRelative);
-            if (!ClassNameRegex.IsMatch(inputBasename))
+            if (!IsValidClassName(inputBasename))
             {
                 throw new RazorCompilerException($"Invalid name '{inputBasename}'. The name must be valid for a C# class name.");
             }
 
             return (resultNamespace, inputBasename);
         }
+
+        private static bool IsValidClassName(string name)
+            => _csharpCodeDomProvider.IsValidIdentifier(name);
     }
 }
diff --git a/src/Microsoft.AspNetCore.Blazor.Build/Microsoft.AspNetCore.Blazor.Build.csproj b/src/Microsoft.AspNetCore.Blazor.Build/Microsoft.AspNetCore.Blazor.Build.csproj
index 6b14171c79..bd671c9af5 100644
--- a/src/Microsoft.AspNetCore.Blazor.Build/Microsoft.AspNetCore.Blazor.Build.csproj
+++ b/src/Microsoft.AspNetCore.Blazor.Build/Microsoft.AspNetCore.Blazor.Build.csproj
@@ -29,6 +29,7 @@
     <PackageReference Include="Microsoft.Extensions.FileProviders.Composite" Version="2.0.0" />
     <PackageReference Include="Microsoft.Extensions.FileProviders.Physical" Version="2.0.0" />
     <PackageReference Include="Mono.Cecil" Version="0.10.0-beta7" />
+    <PackageReference Include="System.CodeDom" Version="4.4.0" />
   </ItemGroup>
 
   <ItemGroup>