Datagrid Bind error

private void bindfunction()
{
int i = 0; int j=0;
SqlDataAdapter da = new SqlDataAdapter(@"select distinct Sectiontype, Questiontype,Subject from dbo.tbl_QuestionConfig where Subject='C++'", con);
DataTable dt = new DataTable();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
for (i = 0, j = 0; i < dataRepeater1.ItemCount && j < dt.Rows.Count; i++,j++)
{

// Label txtExample = (Label)dataRepeater1.Controls.Find("label1", true).First();
//if (txtExample != null)
//{
SqlDataAdapter daa = new SqlDataAdapter(@"select Question,Fullmarks from dbo.tbl_QuestionConfig where Sectiontype='" + dt.Rows[i]["Sectiontype"].ToString() + "' and Questiontype='" + dt.Rows[i]["Questiontype"].ToString() + "' and Subject='" + dt.Rows[i]["Subject"].ToString() + "'", con);
DataTable dtt = new DataTable();
daa.Fill(dtt);
dataGridView1.DataSource = dtt;
dataGridView1.AutoGenerateColumns = false;
dataGridView1.EnableHeadersVisualStyles = false;
dataGridView1.ColumnHeadersDefaultCellStyle.BackColor = Color.LightSeaGreen;
foreach (DataGridViewRow r in dataGridView1.Rows)
{
r.DefaultCellStyle.BackColor = Color.LightCyan;
}

}
}