How to update a gridview column?

how to update a gridview column with session value and Datetime? i have built an update statement

mySql =
"UPDATE BOCStop SET [lftdte] = GETDATE(), [lftusr] = '" +Session["Username"]+ "' WHERE ([cntnum] = '" + @cntnum + "') AND ([blkdte] = '" + @blkdte + "')";
but still GETDATE() has no value.