C# – Mutually exclusive selection of Radiobutton in gridView.ASP.NET C#

    <asp:TemplateField HeaderText="Select One">

    <ItemTemplate>
    <asp:RadioButton ID="RadioButton1" runat="server" />

    </ItemTemplate>

    </asp:TemplateField> 

aspx.cs

protected void Button1_Click(object sender, EventArgs e)
{
    foreach (GridViewRow di in GridView1.Rows)
    {
        RadioButton rad = (RadioButton)di.FindControl("RadioButton1");

        if (rad.Checked&&rad!=null)
        {
            s = di.Cells[1].Text;
        }

    }

    Response.Redirect("applicants.aspx?form=" +s);

}

I'm selecting the rows that are selected with this but I have a problem here I want user to be able to select only one radiobutton but its allowing all the radiobuttons to be selected at once.Can you help me in removing this problem please.
please.