GridView selection by key

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• Live example

Introduction

When using declarative data binding, you will sometimes run into a situation where you need to programmatically set the selection on a GridView control. The problem you may encounter is that the GridView control can only be set by its row index value. Usually, you only possess the key value.

This article demonstrates using an Extension Method to allow you to programmatically set the selected value on a GridView using the key value on the GridView.

The Code

In this example, the dropdown control and the GridView control are bound to the same data source. When the dropdown control is changed, this line is called:

GridView1.SetRowValueValueByKey(DropDownList1.SelectedValue);

This calls the SetRowValueValueByKey Extension Method to set the selected value on the GridView. Below is the complete code for the code-behind:

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace UsingDataKeys
{
    public partial class GridViewSelectionUsingDataKeys : System.Web.UI.Page
    {
        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            GridView1.SetRowValueValueByKey(DropDownList1.SelectedValue);
        }
    }

    public static class GridViewExtensions
    {
        public static void SetRowValueValueByKey(this GridView GridView, 
                                                 string DataKeyValue)
        {
            int intSelectedIndex = 0;
            int intPageIndex = 0;
            int intGridViewPages = GridView.PageCount;
        
            // Loop thru each page in the GridView
            for (int intPage = 0; intPage < intGridViewPages; intPage++)
            {
                // Set the current GridView page
                GridView.PageIndex = intPage;
                // Bind the GridView to the current page
                GridView.DataBind();
                // Loop thru each DataKey in the GridView
                for (int i = 0; i < GridView.DataKeys.Count; i++)
                {
                    if (Convert.ToString(GridView.DataKeys[i].Value) == DataKeyValue)
                    {
                        // If it is a match set the variables and exit
                        intSelectedIndex = i;
                        intPageIndex = intPage;
                        break;
                    }
                }
            }

            // Set the GridView to the values found
            GridView.PageIndex = intPageIndex;
            GridView.SelectedIndex = intSelectedIndex;
            GridView.DataBind();
        }
    }
}

Points of Interest

• You must have the DataValueField set on the GridView for this to work.
• Currently, this code does not handle composite keys; however, it can be modified to do so.