在GridView中使用单选按钮

我有一个RadioButton内的gridview，我使用一个图像按钮切换到下一页和RadioButton值在当前页面与一个隐藏的字段。

但是当我试图检索RadioButton(隐藏字段)中选择的值时，它返回空字符串。

有谁能帮帮我吗?

我的代码如下。

protected void Button1_Click(object sender, EventArgs e)
{
    foreach (GridViewRow gvr in GridView1.Rows)
    {
        RadioButton rb = (RadioButton)gvr.FindControl("RadioButton1");
        if (rb.Checked)
        {
            HiddenField hf = (HiddenField)gvr.FindControl("HiddenField1");
            Response.Write(rb.Text.ToString() + "<br />" + hf.ToString());
        }
        else
        {
            Response.Write("empty<br />");
        }
    }
}
<asp:TemplateField>
   <ItemTemplate>
      <asp:RadioButton ID="RadioButton1" runat="server" onclick="RadioCheck(this);" />
      <asp:HiddenField ID="HiddenField1" runat="server" Value='<%#Eval("Area").ToString()%>' />
   </ItemTemplate>
</asp:TemplateField>
<asp:ImageButton ID="btnEdit" runat="server" OnClick="Button1_Click" ImageUrl="/Images/button.gif" />

protected void Button1_Click(object sender, EventArgs e)
{
foreach (GridViewRow gvr in GridView1.Rows)
   {
    RadioButton rb = (RadioButton)gvr.FindControl("RadioButton1");
    if (rb.Checked)
    {
        HiddenField hf = (HiddenField)gvr.FindControl("HiddenField1");
        Response.Write(rb.Text.ToString() + "<br />" + hf.Value.ToString());
    }
    else
    {
        Response.Write("empty<br />");
    }
}
}