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Use of DataGrid ItemDataBound Event (C#)
By Ranjit Thayyil
A DataGrid ItemDataBound event is raised each time an item (row) is data bound
to the DataGrid. Once this event is raised,
an argument of type DataGridItemEventArgs is passed to the event handling
method and the data relevant to this event is available.
This data is is no longer available once your application exits the event
handling method. The eventhandler for ItemDataBound is
OnItemDataBound.We can specify the method that should handle the event which
takes the event source object
(in our case the datagrid) and the DataGridItemEventArgs as arguments.
This can be explained easily with the help of an example. Consider the
case where you want to calculate the total of a column in a datagrid.
First, let us create a data table and add rows to it with the following C#
code:
protected DataTable dt =
new DataTable("itemprice");
dt.Columns.Add("item",typeof (String));
dt.Columns.Add("price",typeof(float));
DataRow dr; dr = dt.NewRow();
dr["item"]="pen";
dr["price"]=3.5;
dt.Rows.Add(dr);
dr = dt.NewRow();
dr["item"]="camera";
dr["price"]=10.8;
dt.Rows.Add(dr);
dr = dt.NewRow();
dr["item"]="coffee maker";
dr["price"]=40.2;
dt.Rows.Add(dr);
dg.DataSource=dt.DefaultView;
dg.DataBind();< /FONT >
After binding to the datgrid, the display looks like
this:
Since we are using ItemDataBound event to to total
up the price column in the data grid, we
have to
specify on the web form (.aspx) page, the method that would handle the
ItemDataBound event (Event wiring).
This is acheived by mentioning within the datagrid control tag
that on the occurence of the event (OnItemDataBound),
itemDataBound method should be called.
<asp:datagrid id="dg" runat= "server"<
/FONT> OnItemDataBound="itemDataBound"
ShowFooter="True">
On the code behind file (.aspx.cs), we define the
'itemDataBound' method for
handling the
ItemDataBound Event.
float
total = 0;
protected
void itemDataBound(object sender,
DataGridItemEventArgs e)
{
if (e.Item.ItemType!=ListItemType.Header &&
e.Item.ItemType!=ListItemType.Footer)
{
&nbs
p;
total += float.Parse(e.Item.Cells[1].Text);
e.Item.ForeColor = System.Drawing.Color.Blue;
}
else if (e.Item.ItemType == ListItemType.Footer)
{
e.Item.Cells[0].Text = "Total";
e.Item.Cells[1].Text = total.ToString();
}
}
The new datagrid looks like this when rendered on the page:
| item |
price |
| pen |
3.5 |
| camera |
10.8 |
| coffee maker |
40.2 |
| Total |
54.5 |
How does this code work? The itemDataBound
method is called as each row(item) is bound to the datagrid.
Within the method, we check if the current row is a header or a footer
row.To do this we use ListItemType enumeration.
For now, all we need to know is that ListItemType enumeration contains
different types of items(header, footer,item, alternating item etc. )
that can be included in a list control (in our case, a datagrid). Therefore, if
we want to check if the item bound is a datagrid footer,
a simple if statement like this would do the trick:
if (e.Item.ItemType
== ListItemType.Footer) { // your code }
In our method, we add the value in the price column to
the total if the datagrid item is not a header or footer.
Finally, when the
datagrid footer is encountered, we display our total on the footer row of the
datagrid.This is possible because ItemDataBound event
is the last oppurtunity to access the data item before it is displayed in
the browser.
Reference:
MSDN Library - January 2004
If you have any questionsor comments, please feel free to
contact me at ranjiranji@yahoo.com
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