A frequent requirement when using an
ASP.NET GridView on a web page is to have a footer with totals for numeric columns in the GridView. Here is a
GridView subclass that calculates footer totals dynamically. It requires 3 parameters:
FirstComputedColumnIndex - the for index of the first column in the data set to be computed
FirstVisbleComputedColumnIndex - for the index of the first computed column to be shown
NumberOfComputedColumns - for the number of computed columns.
Here is the class code:
namespace Eric.TotalGrid {
public partial class GridView : System.Web.UI.WebControls.GridView
{
private Indexer footerTotals;
public int FirstComputedColumnIndex { get; set; }
public int FirstVisbleComputedColumnIndex { get; set; }
public int NumberOfComputedColumns { get; set; }
protected override void OnLoad(EventArgs e)
{
ShowFooter = true;
base.OnLoad(e);
}
protected override void OnInit(EventArgs e)
{
footerTotals = new Indexer(NumberOfComputedColumns);
InitializeComponent();
base.OnInit(e);
}
private void InitializeComponent()
{
this.RowDataBound += new GridViewRowEventHandler(this.GridView1_RowDataBound);
}
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
DataRowView tableData = e.Row.DataItem as DataRowView;
if (e.Row.RowType == DataControlRowType.DataRow)
{
for (int i = FirstComputedColumnIndex; i < (FirstComputedColumnIndex + NumberOfComputedColumns); i++)
{
if (tableData[i] != DBNull.Value)
{
decimal result = 0;
if (Decimal.TryParse(tableData[i].ToString(), out result))
{
footerTotals[i - FirstComputedColumnIndex] += result;
}
}
}
}
else if (e.Row.RowType == DataControlRowType.Footer)
{
for (int i = 0; i < NumberOfComputedColumns; i++)
{
if (e.Row.Cells.Count > (i + FirstVisbleComputedColumnIndex))
e.Row.Cells[i + FirstVisbleComputedColumnIndex].Text = footerTotals[i].ToString();
}
}
}
}
The key to this GridView is using an
Indexer class that can be accessed like an array. Here is its listing:
class Indexer
{
private int _upperLimit;
private decimal[] myArray;
public Indexer(int limit)
{
_upperLimit = limit;
myArray = new decimal[_upperLimit];
}
public decimal this[int index] // Indexer declaration
{
get
{
// Check the index limits.
if (index < 0 || index >= _upperLimit)
return 0;
else
return myArray[index];
}
set
{
if (!(index < 0 || index >= _upperLimit))
myArray[index] = value;
}
}
}
The
Indexer class can be nested within the
GridView subclass.
The last example shows how to use the custom
GridView on a ASP.NET web page:
First, use the register tag:
<%@ Register Namespace="Eric.TotalGrid" TagPrefix="x" Assembly="TotalGrid" %>
Then, use it just like any other
GridView:
<x:GridView runat="server" ....
FirstComputedColumnIndex="4" FirstVisbleComputedColumnIndex="3" NumberOfComputedColumns="10" >
