Support convention-based DependentUpon for resx files in folders

src/Tasks.UnitTests/CreateCSharpManifestResourceName_Tests.cs

@@ -416,6 +416,39 @@ public void DependentUponConvention_FindsMatch()
             }
         }
 
+        /// <summary>
+        /// Opt into DependentUpon convention and load the expected file properly when the file is in a subfolder.
+        /// </summary>
+        [Fact]
+        public void DependentUponConvention_FindsMatchInSubfolder()
+        {
+            using (var env = TestEnvironment.Create())
+            {
+                var subfolder = env.DefaultTestDirectory.CreateDirectory("SR1");
+                var csFile = subfolder.CreateFile("SR1.cs", "namespace MyStuff.Namespace { class Class { } }");
+                var resXFile = subfolder.CreateFile("SR1.resx", "");
+
+                env.SetCurrentDirectory(env.DefaultTestDirectory.Path);
+
+                ITaskItem i = new TaskItem(@"SR1\SR1.resx");
+                i.SetMetadata("BuildAction", "EmbeddedResource");
+                // Don't set DependentUpon so it goes by convention
+
+                CreateCSharpManifestResourceName t = new CreateCSharpManifestResourceName
+                {
+                    BuildEngine = new MockEngine(_testOutput),
+                    UseDependentUponConvention = true,
+                    ResourceFiles = new ITaskItem[] { i }
+                };
+
+                t.Execute().ShouldBeTrue("Expected the task to succeed.");
+
+                t.ManifestResourceNames.ShouldHaveSingleItem();
+
+                t.ManifestResourceNames[0].ItemSpec.ShouldBe("MyStuff.Namespace.Class", "Expecting to find the namespace & class name from SR1.cs");
+            }
+        }
+
         /// <summary>
         /// Opt into DependentUpon convention without creating the equivalent .cs file for our resource file.
         /// </summary>

src/Tasks/CreateManifestResourceName.cs

@@ -149,9 +149,9 @@ CreateFileStream createFileStream
                     // If opted into convention and no DependentUpon metadata, reference "<filename>.cs" if it exists.
                     if (UseDependentUponConvention && string.IsNullOrEmpty(dependentUpon))
                     {
-                        string conventionDependentUpon = Path.ChangeExtension(fileName, SourceFileExtension);
+                        string conventionDependentUpon = Path.ChangeExtension(Path.GetFileName(fileName), SourceFileExtension);
 
-                        if (File.Exists(conventionDependentUpon))
+                        if (File.Exists(Path.Combine(Path.GetDirectoryName(fileName), conventionDependentUpon)))
                         {
                             dependentUpon = conventionDependentUpon;
                         }