GridView OnClientClick Eval

When working with ASP.NET GridView controls, it is often the case that we need to perform some client-side actions in response to user events. The GridView OnClientClick Eval function provides a means to accomplish this goal.

Overview

The GridView control is a powerful tool for presenting and editing data in an ASP.NET application. However, its default behavior is to perform all actions on the server, which can lead to slow response times and a poor user experience. By using the OnClientClick Eval function, we can trigger custom client-side code in response to user actions, such as button clicks and row selections.

Syntax

The syntax for using the GridView OnClientClick Eval function is as follows:

OnClientClick="<%# Eval('client-side JavaScript code here') %>"

The Eval function is used to evaluate the client-side JavaScript code specified in the GridView OnClientClick attribute. This code can be any valid JavaScript, and can reference any client-side resources, such as jQuery or other JavaScript libraries.

Example

Here is an example of how to use the GridView OnClientClick Eval function to perform client-side validation on a row selection event:

<asp:GridView ID="MyGridView" runat="server" AutoGenerateColumns="False">
    <Columns>
        <asp:BoundField DataField="ID" HeaderText="User ID" ReadOnly="True" />
        <asp:BoundField DataField="Name" HeaderText="User Name" />
        <asp:ButtonField ButtonType="Button" Text="Select" CommandName="Select" 
            OnClientClick="<%# Eval('return validateSelection();') %>" />
    </Columns>
</asp:GridView>

<script type="text/javascript">
    function validateSelection() {
        var name = $('#<%= MyGridView.ClientID %> tr.selected td:nth-child(2)').text();

        if (name === '') {
            alert('Please select a user before proceeding.');
            return false;
        } else {
            return true;
        }
    }

    $(document).ready(function() {
        $('#<%= MyGridView.ClientID %> tr').click(function() {
            $(this).toggleClass('selected');
        });
    });
</script>

In this example, we have added a custom client-side validation function called "validateSelection" to the OnClientClick attribute of a button field. This function is triggered when the user clicks the "Select" button, and checks to ensure that a user has been selected before continuing. If the selection is valid, the function returns true, allowing the server side event to proceed. If the selection is invalid, the function returns false, preventing the server side event from occurring.

Conclusion

The GridView OnClientClick Eval function is a powerful tool for adding custom client-side functionality to GridView controls in ASP.NET applications. By using this function, we can improve the responsiveness and usability of our applications, while providing a more engaging user experience.