Try Like This
<asp:RadioButtonList ID="RadioButtonList1" runat="server" AutoPostBack="True">
<asp:ListItem>Naveen</asp:ListItem>
<asp:ListItem>Kumar</asp:ListItem>
<asp:ListItem>aaaa</asp:ListItem>
</asp:RadioButtonList>
<asp:Button ID="Button6" runat="server" style="height: 26px" Text="Button" />
IN CS:
Protected Sub Button6_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button6.Click
con = New SqlConnection(ConfigurationManager.ConnectionStrings("con").ConnectionString)
If con.State = ConnectionState.Closed Then
con.Open()
End If
da = New SqlDataAdapter("select * from sample where name='" + RadioButtonList1.SelectedItem.Text + "'", con)
ds = New DataSet()
da.Fill(ds)
GridView1.DataSource = ds
GridView1.DataBind()
End Sub