object ref while passing SqlDataReader into DataSet in c#

Hi Sir,

An error is coming while I passing SqlDataReader into DataSet.

Kindly go through the code given below and suggest a solution.

sqlRdr = sqlcmd.ExecuteReader();
while (sqlRdr.Read())
{
dgvFeedBack.DataSource = sqlRdr;
}
if (!sqlRdr.HasRows)
{
RadMessageBox.SetThemeName("Windows7");
RadMessageBox.Show("\nNo Records found between " + dtFromFeedback.Text + " and " + dtToFeedback.Text, "CollectPlus - Du Feedback", MessageBoxButtons.OK, RadMessageIcon.Exclamation);
dgvFeedBack.DataSource = null;
dgvFeedBack.Rows.Clear();
btnExportData.Enabled = false;
}
lblTotalNoOfActions.Text = dgvFeedBack.Rows.Count.ToString();
DsAllFeedback.Tables.Add().Load(sqlRdr);
sqlCon.Close();