Intercept DTE Commands in C#

Here's some sample C# code showing how to intercept DTE commands.  _dispCommandEvents_BeforeExecuteEventHandler has a parameter that allows you to cancel execution of the command if that is what you want to do.

private EnvDTE.CommandEvents mCommandNewProject;

// set up events for IDE commands

cmd = DTE.Commands.Item("File.NewProject", -1);
mCommandNewProject = mDTE.Events.get_CommandEvents(cmd.Guid, cmd.ID);

mCommandNewProject.AfterExecute += new EnvDTE._dispCommandEvents_AfterExecuteEventHandler(CommandNewProject_AfterExecute);

...

Here's the related event handler

// handler for after a new project is opened in the IDE

void CommandNewProject_AfterExecute(string Guid, int ID, object CustomIn, object CustomOut)
{

                //…
}

There is no way to suppress the DTE message box which says that the user is attempting to edit a read-only file.

For more information, see this post in Melody's blog.