Fixed an issue where invalid characters in the path could cause FileExtensionContentTypeProvider.TryGetExtension to throw an exception.

src/Microsoft.AspNet.StaticFiles/FileExtensionContentTypeProvider.cs

@@ -426,7 +426,7 @@ namespace Microsoft.AspNet.StaticFiles
         /// <returns>True if MIME type could be determined</returns>
         public bool TryGetContentType(string subpath, out string contentType)
         {
-            string extension = Path.GetExtension(subpath);
+            string extension = GetExtension(subpath);
             if (extension == null)
             {
                 contentType = null;
@@ -434,5 +434,25 @@ namespace Microsoft.AspNet.StaticFiles
             }
             return Mappings.TryGetValue(extension, out contentType);
         }
+
+        private static string GetExtension(string path)
+        {
+            // Don't use Path.GetExtension as that may throw an exception if there are
+            // invalid characters in the path. Invalid characters should be handled
+            // by the FileProviders
+
+            if (string.IsNullOrWhiteSpace(path))
+            {
+                return null;
+            }
+
+            int index = path.LastIndexOf('.');
+            if (index < 0)
+            {
+                return null;
+            }
+
+            return path.Substring(index);
+        }
     }
 }

test/Microsoft.AspNet.StaticFiles.Tests/DefaultContentTypeProviderTests.cs

@@ -62,5 +62,13 @@ namespace Microsoft.AspNet.StaticFiles
             Assert.True(provider.TryGetContentType(@"\second.css\example.txt", out contentType));
             Assert.Equal("text/plain", contentType);
         }
+
+        [Fact]
+        public void InvalidCharactersAreIgnored()
+        {
+            var provider = new FileExtensionContentTypeProvider();
+            string contentType;
+            Assert.True(provider.TryGetContentType($"{new string(System.IO.Path.GetInvalidPathChars())}.txt", out contentType));
+        }
     }
 }