Radio button does not return selected value
<p>i am using radio button list control in asp.net. 
i m trying to get selected value on button click Event
but,i m getting <code>Empty string</code>  and i want it without javascript.</p>

<p>How can i do this?</p>

<pre><code>&lt;asp:RadioButtonList ID="RadioButtonList1" EnableViewState="true" runat="server" 
    Width="287px"&gt;
&lt;asp:ListItem Value="Single" runat="server" Text="Single"&gt;&lt;/asp:ListItem&gt;
&lt;asp:ListItem Value="Jointly" runat="server" Text="Married Filing Jointly/Widower"&gt;&lt;/asp:ListItem&gt;
&lt;asp:ListItem Value="Separately" runat="server" Text="Married Filing Separately"&gt;&lt;/asp:ListItem&gt;
&lt;asp:ListItem Value="Household" runat="server" Text="Head Of Household "&gt;&lt;/asp:ListItem&gt;
&lt;/asp:RadioButtonList&gt;
</code></pre>

<p>C# code </p>

<pre><code>protected void btnCalculate_Click(object sender, EventArgs e)
{
    string selectedValue = RadioButtonList1.SelectedValue;
}
</code></pre>
