If you haven't assembled your controls in array or list previously, the best you can do is with FindControl
:
int i = 1;
foreach (DataRow row in ds.Rows)
{
Label label = (Label)ParentControlId.FindControl(string.Format("Label{0}", i));
label.Text = row["ques"].ToString();
// same for radio buttons
i++;
}
Note that FindControl
should be called on the direct parent of the label or radio button.