#694 Add an "Open in ILSpy" option to the context menu in the code window

https://github.com/icsharpcode/ILSpy/issues/694

Supports methods, enums, delegates, properties, interfaces, events and classes.

TODO: disambiguate overloaded methods by number and type of parameters

Changes (only) to ILSpy.AddIn project:
add: code window context menu item "Open code in ILSpy"
add: OpenCodeItemInILSpyCallback does the work, using Visual Studio code model to interrogate source at selection point
change: add additional argument support to OpenAssemblyInILSpy (to support "/navigateTo")

ILSpy.AddIn/ILSpyAddIn.vsct

@@ -47,6 +47,10 @@
       <Group guid="guidILSpyAddInCmdSet" id="OpenILSpyProjGroup" priority="0x0200">
         <Parent guid="guidSHLMainMenu" id="IDM_VS_CTXT_PROJNODE"/>
       </Group>
+
+      <Group guid="guidILSpyAddInCmdSet" id="OpenILSpyCodeItemGroup" priority="0x0200">
+        <Parent guid="guidSHLMainMenu" id="IDM_VS_CTXT_CODEWIN"/>
+      </Group>
     </Groups>
     
     <!--Buttons section. -->
@@ -77,6 +81,14 @@
         </Strings>
       </Button>
 
+      <Button guid="guidILSpyAddInCmdSet" id="cmdidOpenCodeItemInILSpy" priority="0x0600" type="Button">
+        <Parent guid="guidILSpyAddInCmdSet" id="OpenILSpyCodeItemGroup" />
+        <Icon guid="guidImages" id="bmpLogo" />
+        <Strings>
+          <ButtonText>Open code in ILSpy</ButtonText>
+        </Strings>
+      </Button>
+
       <Button guid="guidILSpyAddInCmdSet" id="cmdidOpenILSpy" priority="0x0600" type="Button">
         <Parent guid="guidILSpyAddInCmdSet" id="OpenILSpyGroup" />
         <Icon guid="guidImages" id="bmpLogo" />
@@ -114,9 +126,11 @@
       <IDSymbol name="OpenILSpyGroup" value="0x1010" />
       <IDSymbol name="OpenILSpyRefGroup" value="0x1020" />
       <IDSymbol name="OpenILSpyProjGroup" value="0x1030" />
+      <IDSymbol name="OpenILSpyCodeItemGroup" value="0x1040" />
       <IDSymbol name="cmdidOpenILSpy" value="0x0100" />
       <IDSymbol name="cmdidOpenReferenceInILSpy" value="0x0200" />
       <IDSymbol name="cmdidOpenProjectOutputInILSpy" value="0x0300" />
+      <IDSymbol name="cmdidOpenCodeItemInILSpy" value="0x0400" />
     </GuidSymbol>
      
     <GuidSymbol name="guidImages" value="{2f654db9-4641-4638-9937-27c6202b2a6a}" >

ILSpy.AddIn/ILSpyAddInPackage.cs

@@ -77,9 +77,14 @@ namespace ICSharpCode.ILSpy.AddIn
 				mcs.AddCommand(menuItem2);
 
 				// Create the command for the menu item.
-				CommandID menuCommandID3 = new CommandID(GuidList.guidILSpyAddInCmdSet, (int)PkgCmdIDList.cmdidOpenILSpy);
-				MenuCommand menuItem3 = new MenuCommand(OpenILSpyCallback, menuCommandID3);
+				CommandID menuCommandID3 = new CommandID(GuidList.guidILSpyAddInCmdSet, (int)PkgCmdIDList.cmdidOpenCodeItemInILSpy);
+				MenuCommand menuItem3 = new MenuCommand(OpenCodeItemInILSpyCallback, menuCommandID3);
 				mcs.AddCommand(menuItem3);
+
+				// Create the command for the menu item.
+				CommandID menuCommandID4 = new CommandID(GuidList.guidILSpyAddInCmdSet, (int)PkgCmdIDList.cmdidOpenILSpy);
+				MenuCommand menuItem4 = new MenuCommand(OpenILSpyCallback, menuCommandID4);
+				mcs.AddCommand(menuItem4);
 			}
 		}
 		#endregion
@@ -122,6 +127,74 @@ namespace ICSharpCode.ILSpy.AddIn
 			}
 		}
 
+		private void OpenCodeItemInILSpyCallback(object sender, EventArgs e)
+		{
+			var document = (EnvDTE.Document)(((EnvDTE80.DTE2)GetGlobalService(typeof(EnvDTE.DTE))).ActiveDocument);
+			var selection = (EnvDTE.TextPoint)((EnvDTE.TextSelection)document.Selection).ActivePoint;
+			var projectItem = document.ProjectItem;
+
+			string navigateTo = null;
+
+			// Find the full name of the method or class enclosing the current selection.
+			// Note that order of testing is important, need to get the narrowest, most
+			// internal element first.
+			//
+			// Add a prefix to match the ILSpy command line (see doc\Command Line.txt).
+			// The prefix characters are documented in Appendix A of the C# specification:
+			//  E   Event
+			//  F   Field
+			//  M   Method (including constructors, destructors, and operators)
+			//  N   Namespace
+			//  P   Property (including indexers)
+			//  T   Type (such as class, delegate, enum, interface, and struct)
+			navigateTo = GetCodeElementFullName("/navigateTo:M:", projectItem, selection, EnvDTE.vsCMElement.vsCMElementFunction);
+			if (navigateTo == null) {
+				navigateTo = GetCodeElementFullName("/navigateTo:E:", projectItem, selection, EnvDTE.vsCMElement.vsCMElementEvent);
+			}
+			if (navigateTo == null) {
+				navigateTo = GetCodeElementFullName("/navigateTo:P:", projectItem, selection, EnvDTE.vsCMElement.vsCMElementProperty);
+			}
+			if (navigateTo == null) {
+				navigateTo = GetCodeElementFullName("/navigateTo:T:", projectItem, selection,
+					EnvDTE.vsCMElement.vsCMElementDelegate,
+					EnvDTE.vsCMElement.vsCMElementEnum,
+					EnvDTE.vsCMElement.vsCMElementInterface,
+					EnvDTE.vsCMElement.vsCMElementStruct,
+					EnvDTE.vsCMElement.vsCMElementClass);
+			}
+
+			EnvDTE.Project project = projectItem.ContainingProject;
+			EnvDTE.Configuration config = project.ConfigurationManager.ActiveConfiguration;
+			string projectPath = Path.GetDirectoryName(project.FileName);
+			string outputPath = config.Properties.Item("OutputPath").Value.ToString();
+			string assemblyFileName = project.Properties.Item("OutputFileName").Value.ToString();
+
+			// Note that if navigateTo is still null this will just open ILSpy on the assembly.
+			OpenAssemblyInILSpy(Path.Combine(projectPath, outputPath, assemblyFileName), navigateTo);
+		}
+
+		private string GetCodeElementFullName(string prefix, EnvDTE.ProjectItem file, EnvDTE.TextPoint selection, params EnvDTE.vsCMElement[] elementTypes)
+		{
+			foreach (var elementType in elementTypes)
+			{
+				try
+				{
+					var codeElement = file.FileCodeModel.CodeElementFromPoint(selection, elementType);
+					if (elementType == EnvDTE.vsCMElement.vsCMElementFunction)
+					{
+						// TODO: use codeElement.Parameters to disambiguate overloaded methods
+					}
+					return prefix + codeElement.FullName;
+				}
+				catch (COMException)
+				{
+					//Don’t do anything – this is expected if there is no such code element at specified point.
+				}
+			}
+
+			return null;
+		}
+
 		private void OpenILSpyCallback(object sender, EventArgs e)
 		{
 			Process.Start(GetILSpyPath());
@@ -133,13 +206,19 @@ namespace ICSharpCode.ILSpy.AddIn
 			return Path.Combine(basePath, "ILSpy.exe");
 		}
 
-		private void OpenAssemblyInILSpy(string assemblyFileName)
+		private void OpenAssemblyInILSpy(string assemblyFileName, params string[] arguments)
 		{
 			if (!File.Exists(assemblyFileName)) {
 				ShowMessage("Could not find assembly '{0}', please ensure the project and all references were built correctly!", assemblyFileName);
 				return;
 			}
-			Process.Start(GetILSpyPath(), Utils.ArgumentArrayToCommandLine(assemblyFileName));
+
+			string commandLineArguments = Utils.ArgumentArrayToCommandLine(assemblyFileName);
+			if (arguments != null) {
+				commandLineArguments = string.Concat(commandLineArguments, " ", Utils.ArgumentArrayToCommandLine(arguments));
+			}
+
+			Process.Start(GetILSpyPath(), commandLineArguments);
 		}
 
 		private void ShowMessage(string format, params object[] items)

ILSpy.AddIn/PkgCmdID.cs

@@ -9,5 +9,6 @@ namespace ICSharpCode.ILSpy.AddIn
 		public const uint cmdidOpenILSpy = 0x100;
 		public const uint cmdidOpenReferenceInILSpy = 0x200;
 		public const uint cmdidOpenProjectOutputInILSpy = 0x300;
+		public const uint cmdidOpenCodeItemInILSpy = 0x0400;
 	};
 }

ILSpy.AddIn/Utils.cs

@@ -74,6 +74,10 @@ namespace ICSharpCode.ILSpy.AddIn
 
 		static void AppendArgument(StringBuilder b, string arg)
 		{
+			if (arg == null) {
+				return;
+			}
+
 			if (arg.Length > 0 && arg.IndexOfAny(charsNeedingQuoting) < 0) {
 				b.Append(arg);
 			} else {