Juknum.Windows.ContextMenu

A .NET library for building Windows Explorer context menu handlers with IExplorerCommand. This library is intended for .NET developers who want to add custom commands to the Windows Explorer context menu without having to implement the COM plumbing themselves.

Targets & Dependencies

The library depends on Vanara.PInvoke.Shell32 for the Explorer COM interfaces and shell types.

Overview

The library focuses on three pieces:

• Single commands through ExplorerCommand
• Submenu / grouped commands through ExplorerCommandMenu
• Registry registration helpers through RegistrationHelper

ExplorerCommand

Handles the COM-facing IExplorerCommand implementation and maps it to a simpler override-based API.

Member	Purpose	Notes
Guid	Identifies the command handler	Used as the COM CLSID for the command. Should be the same as the Guid() Attribute on top of the implementing class.
Title	Name shown in Explorer	This is the text users see in the context menu
Icon	Optional shell icon reference	Return null to omit an icon
ToolTip	Optional informational text	The base type exposes it, but Explorer does not use it directly
IsEnabled(...)	Determines whether the command is enabled	Return false to disable the item for the current selection
Execute(...)	Runs the command action	Return true when the command succeeds

Example

[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[Guid("...")]
internal class ContextMenuCommandHelloWorld : ExplorerCommand {
	public override Guid Guid => new("...");
	public override string Title => "Hello World";

	public override bool Execute(IShellItemArray psiItemArray, IBindCtx? pbc) {
		MessageBox.Show("Hello, World!");
		return true;
	}
}

Note

The GUID is used as the COM CLSID for the command. It is recommended to generate a new GUID for the main registered class (e.g: E3629D56-49C1-41F8-B7EF-0057EE60126C) and use derived GUIDs (e.g: E3629D56-0001-0001-0001-000000000001) for any child commands

ExplorerCommandMenu

Builds on top of ExplorerCommand, this class is useful when you want to create a submenu in the Explorer context menu. It exposes a Commands array and uses the internal command enumerator to surface child items to Explorer.

Member	Purpose	Notes
Guid	Identifies the command handler	Used as the COM CLSID for the command. Should be the same as the Guid() Attribute on top of the implementing class.
Title	Name shown in Explorer	This is the text users see in the context menu
Icon	Optional shell icon reference	Return null to omit an icon
ToolTip	Optional informational text	The base type exposes it, but Explorer does not use it directly
IsEnabled(...)	Determines whether the command is enabled	Return false to disable the item for the current selection
Commands	Child commands shown under the menu	Return an array of IExplorerCommand instances

Example

[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[Guid("...")]
internal class ContextMenuExample : ExplorerCommandMenu {

	public override Guid Guid => new("...");
	public override string Title => "Example Context Menu";
	public override IExplorerCommand[] Commands => [
		new ContextMenuCommandHelloWorld(),
	];
}

RegistrationHelper

A static helper class that writes the registry entries that Explorer uses to discover a command handler. It supports registration for:

• All files
• Directories
• Directory background
• Optional extension-specific verbs

Use RegistrationHelper.RegisterCommand(...) from your COM registration hook to create the Explorer registry entries for your command handler.

The helper takes a verb name, display label, and CLSID, plus optional scope flags:

• allFiles: true registers under *\shell
• allFolders: true registers under Directory\shell and Directory\Background\shell
• extension: ".txt" registers for a specific file type

UnregisterCommand(...) removes the same verb from the common locations.

[ComRegisterFunction]
public static void Register(Type type) {
	RegistrationHelper.RegisterCommand(
		verbName: "ExampleContextMenu",
		menuLabel: "Example Context Menu",
		clsid: type.GUID.ToString("B"),
		allFiles: true,
		allFolders: true
	);
}

Important

Only the top-level command or menu class should define the static Register and Unregister methods. Child commands that are returned from ExplorerCommandMenu.Commands should stay as plain command implementations and should not register themselves separately.

Example Project

The sample project in src/Windows.ContextMenuExample shows one concrete way to wire the library together.

Notes

• The runtime behavior is Windows-only because the API is built around Explorer COM interfaces.
• Icon should return a shell-compatible icon reference, such as an assembly resource path, e.g. @"C:\Path\To\MyAssembly.dll,-123". The -123 is the resource ID of the icon in the DLL. You can also use .ico files or other shell-supported icon formats.