How to drag a LABEL control from the Toolbox into a PICTUREBOX control.

Hi,
I have a windows application which have all functionality of Microsoft Visual Studio. In this application we have it's own LABEL, PICTUREBOX, TEXTBOX,..,

My question is that when i drag LABEL from ToolBox and put some where else on the application surface, After that select LABEL on application surface and drag and drop on PICTUREBOX it work fine.

But when i drag LABEL from ToolBox and drop it on PICTUREBOX, it is not work.

I have this.pictureBox1.AllowDrop = true; property,