c# - How to recognize if a rectangle contains a Text block within in -

i'm creating program in user drags/drops text block rectangle, , store contents of specific textblock when he/she drops rectangle.

i figured out how drag/drop, can't figure out how check if rectangle contains textblock.

here's code far:

bool captured = false; double x_shape, x_canvas, y_shape, y_canvas; uielement source = null;    private void shape_mouseleftbuttondown(object sender, mousebuttoneventargs e) {   source = (uielement)sender;   mouse.capture(source);   captured = true;   x_shape = canvas.getleft(source);   x_canvas = e.getposition(layoutroot).x;   y_shape = canvas.gettop(source);   y_canvas = e.getposition(layoutroot).y; }  private void shape_mousemove(object sender, mouseeventargs e) {   if (captured)   {     double x = e.getposition(layoutroot).x;     double y = e.getposition(layoutroot).y;     x_shape += x - x_canvas;     canvas.setleft(source, x_shape);     x_canvas = x;     y_shape += y - y_canvas;     canvas.settop(source, y_shape);     y_canvas = y;   } }  private void shape_mouseleftbuttonup(object sender, mousebuttoneventargs e) {   mouse.capture(null);   captured = false; }    private void rectangle1_mouseenter(object sender, mouseeventargs e) {     if (mouse.capture(null))     {         textbox1.text = "test";       } } 

the "shape" events apply textblock way, clarification. tried find shortcut , make rectangle1_mouseenter event if mouse isn't clicked, store values (didn't include code storing values). however, problem is, idea doesn't work because textbox1.text="test" isn't registered, , don't see why isn't.