Get DataKey value on SelctedIndexChanged event of DropDownList in GridView ASP.Net

Ref:

How-to-bind-data-to-a-DropDownList-which-is-inside-a-GridView-in-ASPNet.aspx

I have added OnSelectedIndexChanged event to DropDownList with AutoPostBack to True.

Also added the DataKeyNames with ContactName in GridView.

HTML

<asp:GridView ID="GridView1" runat="server" DataKeyNames="ContactName" AutoGenerateColumns="false"
    OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:BoundField HeaderText="Name" DataField="ContactName" />
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Country") %>' Visible="false" />
                <asp:DropDownList ID="ddlCountries" runat="server" OnSelectedIndexChanged="Countries_OnSelectedIndexChanged" AutoPostBack="true">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

C#

protected void Countries_OnSelectedIndexChanged(object sender, EventArgs e)
{
    GridViewRow row = (sender as DropDownList).NamingContainer as GridViewRow;
    string dataKey = this.GridView1.DataKeys[row.RowIndex].Value.ToString();
}

Rest of the code will remain same.