Copying from the selected textbox in visual studio 2013 C++

[UberProgrammer]

Hey,
I am adding a menu strip to my windows forum application and I want to copy from the active textbox. This is the code for the event, I tried to cast the return of GetActiveWindow (a handle) to a textbox:

	System::Void ResearchHelper::copyToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e){//Edit->Copy
		TextBoxBase^ currentBox = (TextBoxBase^)GetActiveWindow;
		currentBox->Copy();
	}

I get "invalid type conversion", so I obviously can't go this route. How should this be done?