how to multiply a grideview column with a text box

Hi,

Use the row databound method of gridview and into this method find the control of the gridview cell and then multiply the textbox value with the cell value.

void GridView_RowDataBound(Object sender, GridViewRowEventArgs e)
 {
   if(e.Row.RowType == DataControlRowType.DataRow)
   {
     // Multiply the cell of gridview with the textbox value.
     e.Row.Cells[1].Text = (Convert.ToInt32(e.Row.Cells[1].Text) + Convert.ToInt32(textBox.Text)).ToString(); //put the cell number as position in your gridview
   }

 }

In the gridview add the below event.

<asp:gridview id="GridView" onrowdatabound="GridView_RowDataBound" runat="server">
//Your gridview code



Hope this will help you