whenever textblock is clicked and being edited the the other node position get changes. How can fix this problem that when text block is in editable mode it should change it position.
You are talking about the value of Node.location, aren’t you?
First, it should be clear that the location of the Node whose TextBlock is being edited does not change while the text editor is active.
Second, during text editing the edited TextBlock.text does not change. It is only set once the TextEditingTool completes successfully. Thus it is only after an edit has been accepted that the size of a Node might change, thereby (normally) invalidating the Layout, and thus causing some nearby nodes to be moved by the layout.