C# window form application

Question

Hello Team, Please I have this error in my C# window form application which says the multi-part identifier "System.Data.DataRowView could not be bound, Kindly help.

private void cmbRoom_SelectedIndexChanged(object sender, EventArgs e)
{
if(cmbRoom.SelectedIndex !=-1)
{
string qry = @"Select rRate from tblRoom where roomID ="+cmbRoom.SelectedValue+"";
SqlCommand cmd = new SqlCommand(qry,MainClass.con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
txtRate.Text = dt.Rows[0]["rRate"].ToString();
}
}
???????}