具有网格行高的RichTextBox高度绑定在xaml编辑器中工作，但在程序中不起作用

In fact, I simply want to bind the height of RichTextBox to the height of the row in the grid, in a WPF application using VS 2015 community. And according to the XAML editor window, it did work, but when I launch the program/debug, it doesn't show the same result. Here is the code :In fact, I simply want to bind the height of Ri