Happy Coding: Check/uncheck CheckBox in a GridView using Javascript

Introduction

Check/uncheck CheckBox control inside a GridView using javascript without postback. This article will give an idea on how to achieve this task.

Some sample code is provided under Using the code heading and complete code is available in the project download.

Background

(Forums are flooded with the questions about how to check/uncheck CheckBox control inside a GridView using javascript without postback.

How To’s:

In this article a GridView control is used. Inside the GridView control there are 3 fields. One template field and two are bound fields to display some sample data.

Inside the TemplateField a CheckBox control is placed in the HeaderTemplate (with ID cbSelectAll and Text Select All), ItemTemplate and AlternatingItemTemplate.

Using the code

Code that will be required to achieve this task.
Javascript that will be required to perform the Select All action is as follow:

    <script type="text/javascript">
        function SelectAll(id)
        {
            //get reference of GridView control
            var grid = document.getElementById("<%= GridView1.ClientID %>");
            //variable to contain the cell of the grid
            var cell;
            
            if (grid.rows.length > 0)
            {
                //loop starts from 1. rows[0] points to the header.
                for (i=1; i<grid.rows.length; i++)
                {
                    //get the reference of first column
                    cell = grid.rows[i].cells[0];
                    
                    //loop according to the number of childNodes in the cell
                    for (j=0; j<cell.childNodes.length; j++)
                    {           
                        //if childNode type is CheckBox                 
                        if (cell.childNodes[j].type =="checkbox")
                        {
                        //assign the status of the Select All checkbox to the cell checkbox within the grid
                            cell.childNodes[j].checked = document.getElementById(id).checked;
                        }
                    }
                }
            }
        }
    </script>

Code required to add an attribute of cbSelectAll CheckBox is as follow:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //Binding GridView with the datasource

            //FillDataTable is a method that will return a DataTable
            //filled with some rows (code available in download)
            this.GridView1.DataSource = FillDataTable();
            this.GridView1.DataBind();
        }
    }

    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.Header)
        { 
            //Find the checkbox control in header and add an attribute
            ((CheckBox)e.Row.FindControl("cbSelectAll")).Attributes.Add("onclick", "javascript:SelectAll('" + 
                    ((CheckBox)e.Row.FindControl("cbSelectAll")).ClientID + "')");
        }
    }