title: there is no row at position 1
body: <p>i'm creating a window form and i run this code ,firsttime i was add avalue in datagirdview correctly but the secondtime i'm trying to add a value in datagirdview but getting this error </p>
  
  <p>There is no row at position 1. 
  this line </p>
  
  <pre><code>        double b = Convert.ToDouble(dt.Rows[count][1]);
  
          int count = 0;
  
          private void button1_Click(object sender, EventArgs e)
          {
              id = Convert.ToInt32(txt_item.Text);
  
              date = DateTime.Now;
  
          string q = "select pro_name , amount from Product where pro_id =  " + id ;
          dt = g.selectQuery(q);            
  
          if (dt.Rows.Count &gt; 0)
          {
              if (!dt.Columns.Contains("Quantity selected"))
              {
                  dt.Columns.Add("Qty");
              }
              if (!dt.Columns.Contains("Total"))
              {
                  dt.Columns.Add("Total");
              }               
              double b = Convert.ToDouble(dt.Rows[count][1]);
              dt.Rows[count][2] = 1;
              dt.Rows[count][3] =  1*b;                
              dataGridView1.DataSource = dt;
              count++;
  
              }
  }
  </code></pre>