>I place a CheckBox in a grid column. The problem is that checkbox shows up at the left side of the cell. How can I make it to display in the center? Thanks in advance.

You need to put it into a container first, then add the container to the column. Before adding the container, though, make it about the same size as the grid column cell where it'll go, and then adjust the checkbox so it's centered in the container. It's a little trial & error after that with checkbox top & left, but not much...