I think i had the same problem. I had the problem, that I set my datagrid to a fixed width (so when only two columns are added, it does not look so skinny). But then it looked like if i had an extra empty column (took me a while to realize that it was not
really a column) :)
Here is how I fixed the problem. The answer above is right, but when adding the columns programatically, try the following:
int i=1;<font size="2">
col in datagrid.Columns)
this sets the column with to "1*".
Then the columns spanned the whole grid and I did not see an artificial empty column.