Input string was not in a correct format in gridview computation of cells

Question

I tried to do the computation in this link but it says that input string was not in a correct format. I am computing values of cells in the gridview. Here is my code:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    int tot = 0;
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
          decimal medjtot = (Convert.ToInt32(e.Row.Cells[3].Text) * (Convert.ToDecimal(e.Row.Cells[4].Text) / 12)) * Convert.ToDecimal(e.Row.Cells[5].Text);
          Label RowTotal = (Label)e.Row.FindControl("Label1");
          RowTotal.Text = medjtot.ToString();    
    }
 }

Answer 1

Make sure you do a guard check on your Text property for each Row Cell. It is possible that the text is whitespace or empty.

Sample guard check.

   if(string.IsNullOrWhiteSpace(e.Row.Cells[5].Text) || 
       string.IsNullOrWhiteSpace(e.Row.Cells[3].Text))
          return;

Answer 2

Must be on this line :

decimal medjtot = (Convert.ToInt32(e.Row.Cells[3].Text) * (Convert.ToDecimal(e.Row.Cells[4].Text) / 12)) * Convert.ToDecimal(e.Row.Cells[5].Text);

If your cells contain forbiden characters (letter for an int32 for example) the conversion will fail. Check also the culture, the separator for decimal may be a coma or a dot.