Delete, will cause the GridView to delete the associated row when pressed.  Since our aim is to show a confirmation message before the deletion of the row, we will also make use of the button's OnClientClick property.

The button control's properties are assigned as follows:

·         OnClientClick to JavaScript confirm message

·         CommandNameto Delete

The DataKeyNames property of the GridView control is used to specify the field or fields that represent the primary key of the data source.

Listing 1 – Display Data Using GridView Control

 
Code:
 
<asp:GridView ID="GridView1"runat="server" 
DataSourceID="SqlDataSource1" 
AutoGenerateColumns="False" 
DataKeyNames="EmployeeId">
<Columns>
<asp:TemplateField HeaderText="Delete">
<ItemTemplate>
   <asp:Button ID="btnDelete" Text="Delete" runat="server"
OnClientClick="return confirm('Are you sureyou want to delete this record?');"
CommandName="Delete" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField HeaderText="EmployeeId" DataField="EmployeeId" />
<asp:BoundField HeaderText="FirstName" DataField="FirstName" />
<asp:BoundField HeaderText="LastName" DataField="LastName" />
</Columns>
</asp:GridView>
 
Next, we set the SqlDataSource DeleteCommand and its parameters.  EmployeeId is the primary key in the Employees table.  This key is used to delete the row.  The GridView needs to find which row has to be deleted, hence we used @original_EmployeeId and not @EmployeeId.  If we don't prefix this parameter with original_ then there is no way to find that row which has to be deleted.

Listing 2 – The SqlDataSource

 
Code:
 
<asp:SqlDataSource ID="SqlDataSource1"runat="server" 
ConnectionString="Server=localhost;Database=Northwind;userid=username;password=secret;" 
SelectCommand="Select * from Employees" 
DeleteCommand="Delete from Employees whereEmployeeId=@original_EmployeeId"
OnDeleted="SqlDataSource1_Deleted">
<DeleteParameters>
<asp:Parameter Type="Int32"Name="EmployeeId"></asp:Parameter>
</DeleteParameters>
</asp:SqlDataSource>
<asp:Label ID="lblShow"runat="server" ForeColor="DarkRed"></asp:Label>
 
To show a message to the end user after the row has been deleted we will use the Deleted event of the SqlDataSource control to do this task for us and also supply and error messages.

Listing 3 - The Deletion Code

C#

protected void SqlDataSource1_Deleted(objectsender,
  SqlDataSourceStatusEventArgs e)
{
  if (e.Exception == null)
  {
    if (e.AffectedRows == 1)
    {
      lblShow.Text = "Record deletedsuccessfully.";
    }
    else
    {
      lblShow.Text = "An error occurredduring the delete operation.";
    }
  }
  else
  {
    lblShow.Text = "An error occurred whileattempting to delete the row.";
    e.ExceptionHandled = true;
  }

<asp:GridView DataKeyNames="CategoryID" ID="GridView1" 
       runat="server" AutoGenerateColumns="False" 
       OnRowCommand="GridView1_RowCommand" 
       OnRowDataBound="GridView1_RowDataBound" 
       OnRowDeleted="GridView1_RowDeleted" OnRowDeleting="GridView1_RowDeleting">
  <Columns>
   <asp:BoundField DataField="CategoryID" HeaderText="CategoryID" />
   <asp:BoundField DataField="CategoryName" HeaderText="CategoryName" />
   <asp:TemplateField HeaderText="Select">
     <ItemTemplate>
       <asp:LinkButton ID="LinkButton1" 
         CommandArgument='<%# Eval("CategoryID") %>' 
         CommandName="Delete" runat="server">
         Delete</asp:LinkButton>
     </ItemTemplate>
   </asp:TemplateField>
  </Columns>
</asp:GridView>

protected void GridView1_RowDataBound(object sender, 
                         GridViewRowEventArgs e)
{
  if (e.Row.RowType == DataControlRowType.DataRow)
  {
    LinkButton l = (LinkButton)e.Row.FindControl("LinkButton1"); 
    l.Attributes.Add("onclick", "javascript:return " +
    "confirm('Are you sure you want to delete this record " +
    DataBinder.Eval(e.Row.DataItem, "CategoryID") + "')"); 
  }
}

protected void GridView1_RowCommand(object sender, 
                         GridViewCommandEventArgs e)
{
  if (e.CommandName == "Delete")
  {
    // get the categoryID of the clicked row
    int categoryID = Convert.ToInt32(e.CommandArgument);
    // Delete the record 
    DeleteRecordByID(categoryID);
    // Implement this on your own :) 
  }
}

<asp:GridView DataKeyNames="CategoryID" ID="GridView1" 
     runat="server" AutoGenerateColumns="False" 
     OnRowCommand="GridView1_RowCommand" 
     OnRowDataBound="GridView1_RowDataBound"
     OnRowDeleted="GridView1_RowDeleted" 
     OnRowDeleting="GridView1_RowDeleting">

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
  int categoryID = (int) GridView1.DataKeys[e.RowIndex].Value;
  DeleteRecordByID(categoryID); 
}