Insertcommand @value Null...

My problem is when trying to insert it's coming back that "Column 'textmenu' cannot be null" who is right for that fieldCode below: 
<script language="vb" runat="server">


    sub Page_Load(s as Object, e as EventArgs)
        if ( Page.IsPostBack ) then
            Exit sub
        end if

    end sub

    private sub SubmitBtn_Click(s As Object, e As EventArgs)
        SqlDataSource1.Insert()
    end sub

</script>


    <asp:sqldatasource id="SqlDataSource1" runat="server"
        ConnectionString="<%$ ConnectionStrings:test %>" ProviderName="<%$ ConnectionStrings:test.ProviderName %>"
            insertcommand="INSERT INTO test (textmenu) VALUES (@somevalue)">

        <insertparameters>
            <asp:ControlParameter PropertyName="text" ControlID="CompanyNameBox" Name="somevalue" Type="String" />
        </insertparameters>

    </asp:sqldatasource>

    <asp:textbox id="CompanyNameBox" runat="server" />
    <asp:Button id="submitButton" Text="Envoyer" OnClick="SubmitBtn_Click" runat="server"/>


</asp:Content>
 
So I change the constrain to accept "null" value then I check in the table database and there is a record but no value
So I change the sql command to "INSERT INTO test (textmenu) VALUES ('test')" and it's working I have a record and the value "test" in the table
I don't know what I'm doing wrong up here with the @value. Can anyone help?
 Thanks