If you are using Gridview, you can do this by implementing your code in
GridView1_RowDataBound(...)
function
find your control here:
CheckBox chk = (CheckBox)e.Row.Cells[0].FindControl("chk1");
Put the checkbox property checked true based on your condition:
if (e.Row.Cells[1].Text.ToString() == "Yes")
{
chk.Checked = true;
}