Dynamically assign DataKeyNames to GridView using C# and VB.net in ASP.Net

comunidadmexicana says:

gvProducts.DataKeyNames = "tkt"; //line error

You need to set string array to DataKeyNames.

So you need to convert the value to string array.

gvProducts.DataKeyNames = new string[] { "tkt"};

Refer below sample.

HTML

<asp:GridView runat="server" ID="gvCustomers"></asp:GridView>
<hr />
<asp:TextBox runat="server" ID="txtDataKey" /><br/><br/>
<asp:Button Text="Set Key Name" runat="server" OnClick="OnSet" />
<asp:Button Text="Get Key Name" runat="server" OnClick="OnGet" />

Namespace

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        BindGrid();
    }
}

private void BindGrid()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] {
                        new DataColumn("CustomerId", typeof(int)),
                        new DataColumn("Name", typeof(string)),
                        new DataColumn("Country",typeof(string)) });
    dt.Rows.Add(1, "John Hammond", "United States");
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(4, "Robert Schidner", "Russia");
    gvCustomers.DataSource = dt;
    gvCustomers.DataBind();
}

protected void OnSet(object sender, EventArgs e)
{
    gvCustomers.DataKeyNames = new string[] { txtDataKey.Text.Trim() };
    BindGrid();
}

protected void OnGet(object sender, EventArgs e)
{
    ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "alert('Key Name : " + gvCustomers.DataKeyNames.GetValue(0) + "');", true);
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        BindGrid()
    End If
End Sub

Private Sub BindGrid()
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {
                        New DataColumn("CustomerId", GetType(Integer)),
                        New DataColumn("Name", GetType(String)),
                        New DataColumn("Country", GetType(String))})
    dt.Rows.Add(1, "John Hammond", "United States")
    dt.Rows.Add(2, "Mudassar Khan", "India")
    dt.Rows.Add(3, "Suzanne Mathews", "France")
    dt.Rows.Add(4, "Robert Schidner", "Russia")
    gvCustomers.DataSource = dt
    gvCustomers.DataBind()
End Sub

Protected Sub OnSet(ByVal sender As Object, ByVal e As EventArgs)
    gvCustomers.DataKeyNames = New String() {txtDataKey.Text.Trim()}
    BindGrid()
End Sub

Protected Sub OnGet(ByVal sender As Object, ByVal e As EventArgs)
    ClientScript.RegisterClientScriptBlock(Me.GetType(), "alert", "alert('Key Name : " & gvCustomers.DataKeyNames.GetValue(0) & "');", True)
End Sub

Screenshot