radio button always return false

hello sorry for my english i use a radio button and i need change checked value to false or true in the page load method, my problem is, when i click in a button to send and save selection values in my form, radio buttons always return false this is my code

Front-end Code:

Code:

---

<ext:Button ID="btnGuardarTop" runat="server" Icon="DiskBlack" Text="Guardar" OnDirectClick="btnGuardar_Click">
    </ext:Button>
    <ext:Radio ID="V1213" runat="server" BoxLabel="CON GRUPO" Name="mismo" />
    <ext:Radio ID="V1214" runat="server" BoxLabel="SIN GRUPO" Name="mismo" />

---

Codebehind:

Code:

---

protected void Page_Load(object sender, EventArgs e)
    {
        if (!X.IsAjaxRequest)
        {
            V1213.Checked = false;
        }
    }
    protected void btnGuardar_Click(object sender, DirectEventArgs e)
    {
        int intVal;
        if (this.V1213.Checked)
            intVal = 1;
    }

---