GridView Delete, with Confirmation

Introduction

Everyone likes a confirmation that lets them know that a record is being deleted. In this article, I will show you how you can prompt confirmation boxes when you delete a record from the GridView control.

Implementing the Confirmation Feature

The first thing that you need to do is to attach the JavaScript confirmation code to the delete column of the GridView control. This can be done in the Row_DataBound event of the GridView control. The Row_DataBound event is fired whenever the row is attached to the GridView. Hence, this is fired when the GridView is building for the first time or even when the page is reloaded.

Let's see the HTML part of the GridView code:

<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>

As you can see from the above code, I have three columns in the GridView. Columns CategoryID and CategoryName are the bound columns, and the column Delete is a template column. The command argument is set as the CategoryID which means that whenever the LinkButton is clicked, it will pass CategoryID as an argument. The CommandName is set to "Delete".

The CommandName property is very important. If you have a LinkButton or a Button control inside the template column of the GridView control and the CommandName property is set to "Delete", then apart from GridView_RowCommand event, the GridView_Row_Deleting event is also fired.

Now, let's see the GridView_RowBound event where I attach the JavaScript code to every LinkButton.

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") + "')"); 
  }
}

In the above code, I checked whether the GridView row is a DataRow, and if it is, I simply attach some JavaScript code using the Attributes.Add method.

Catching the Primary Key of the Clicked Row

Now that you have successfully attached the JavaScript code to the GridView control, all that is left is to catch the primary key of the row which you have clicked so that you can perform further operations (like deleting the row). Remember what I said about a LinkButton or a Button control with the CommandName set to "Delete"? If you don't, read the text in the box again.

The CommandName property is very important. If you have a LinkButton or a Button control inside the template column of the GridView control and the CommandName property is set to "Delete", then apart from the GridView_RowCommand event, the GridView_Row_Deleting event is also fired.

Now, since our LinkButton's CommandName is set to "Delete", it means we have two choices of getting the primary key from the GridView. We can do this in the RowCommand event, or we can do this in the Row_Deleting event. I am going to show you both of them.

Catching the primary key in the RowCommand event

This is pretty simple. All you need to do is to get the value from the CommandArgument property which you have already set to the 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 :) 
  }
}

e.CommandArgument returns object so you need to convert it to int as I have done above.

Catching the primary key in the Row_Deleting event

Let's see how we can catch the primary key of the clicked row in the Row_Deleting event.

<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); 
}

In the above technique, you must set the DataKeyNames property of the GridView to "CategoryID". The GridView1.DataKeys[e.RowIndex].Value property gets the CategoryID out of the row which is clicked.

I hope you liked this article, happy coding!

注：
除了以上两种方法，还在网上看到了这种方法，不过我还没有测试：
<asp:GridView ID="GridView1" runat="server" DataKeyNames="id" DataSourceID="SqlDataSource1">

<Columns>

   <asp:TemplateField ShowHeader="False">

     <ItemTemplate>

       <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False" CommandName="Delete"

                    OnClientClick='return confirm("Are you sure you want to delete this entry?");'

                    Text="Delete" />

     </ItemTemplate>

   </asp:TemplateField>

</Columns>

</asp:GridView>