How to perform multiplication on two column for datagrid view and assigning it in third column?

Question

Here is my code, I am trying to display multiplication of Rate * Supply column values and assigning it to the Amount column in data grid view :

try
{
    Query = "Select  id,Code,Description,Rate,Cust_Id,Supply,Empty,Amount,Received from Items ";
    adap = new SQLiteDataAdapter(Query, GlobalVars.conn);
    ds = new DataSet();
    adap.Fill(ds, "Items");
    dtgVOuchers.DataSource = ds.Tables[0];

    ds.Tables[0].Columns["Amount"].DefaultValue = (ds.Tables[0].Columns["Rate"].DefaultValue) * (ds.Tables[0].Columns["Supply"].DefaultValue); //error

    //dtgVOuchers.Rows.Clear();
    ds.Tables[0].Clear();
    dtgVOuchers.Refresh();
}

Does anyone know how I can accomplish this functionality in data grid view ? . .Please help me to correct this code. Thanks

Answer 1

            foreach (DataGridViewRow row in dtgVOuchers.Rows)
            {
                row.Cells[dtgVOuchers.Columns["Amount"].Index].Value = (Convert.ToDouble(row.Cells[dtgVOuchers.Columns["Rate"].Index].Value) * Convert.ToDouble(row.Cells[dtgVOuchers.Columns["Supply"].Index].Value));

            } 

Answer 2

just use the query

Select  id,Code,Description,Rate,Cust_Id,Supply,Empty,isnull(Rate,0)*isnull(Supply,0) as [Amount],Received from Items 

Answer 3

DataTable myDataTable = new DataTable();

      DataColumn quantityColumn = new DataColumn("Quantity");
      DataColumn rateColumn = new DataColumn("Rate");
      DataColumn priceColumn = new DataColumn ("Price");

      quantityColumn.DataType = typeof(int);
      rateColumn.DataType = typeof(int);

      myDataTable.Columns.Add(quantityColumn);
      myDataTable.Columns.Add(rateColumn);
      myDataTable.Columns.Add(priceColumn);

      //Set the Expression here
      priceColumn.Expression = "Quantity * Rate";

Answer 4

Use the below code..run a loop to update the Amount column in all rows

Note : Though this method is not preferred as it effects performance.So do this calculation in the sql query.I dont understand the reason behind not doing the munltiplication in SQL query..

  foreach (DataRow row in ds.Tables[0].Rows)
       {
          row["Amount"]= Convert.ToDecimal(row["Rate"])* Convert.ToDecimal(row["Supply"]);
          ds.Tables[0].AcceptChanges();        
       } 
    dtgVOuchers.DataSource = ds.Tables[0];
    dtgVOuchers.Refresh();