Buyrun sanırım size yardımcı olur ...

<%@ Page Language="VB" AutoEventWireup="true" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    Sub Page_Load()
        If Not Page.IsPostBack Then
            Response.Write("Herhangi Bir Checkbox Secilmedi")
        End If
        Dim secilen As String
        secilen = " "
        If CheckBox1.Checked Then secilen = secilen + CheckBox1.Text
        If CheckBox2.Checked Then secilen = secilen + CheckBox2.Text
        If CheckBox3.Checked Then secilen = secilen + CheckBox3.Text
        If CheckBox4.Checked Then secilen = secilen + CheckBox4.Text
        If CheckBox5.Checked Then secilen = secilen + CheckBox5.Text
        If CheckBox6.Checked Then secilen = secilen + CheckBox6.Text
        Response.Write(secilen)
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Checkbox</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:CheckBox ID="CheckBox1" runat="server" Text="İngilizce" />
        <asp:CheckBox ID="CheckBox2" runat="server" Text="Almanca" />
        <asp:CheckBox ID="CheckBox3" runat="server"  Text="İtalyanca"/><br />
        <asp:CheckBox ID="CheckBox4" runat="server" Text="Fransızca" />
        <asp:CheckBox ID="CheckBox5" runat="server" Text="İspanyolca" />
        <asp:CheckBox ID="CheckBox6" runat="server" Text="Türkçe" /></div>
        <asp:Button ID="Button1" runat="server" Text="Gönder" />
    </form>
</body>
</html>