CustomValidator don't see OnServerValidate function

Question

I created CustomValidator, but it don't see function BookingTypeS4AProjects_Validate when I debug it.

ClassA.ascx

<asp:DropDownList 
    ID="ddlProjects" 
    runat="server"
    Width="450"
    DataSourceID="odsProjects" 
    DataTextField="ProjName"
    DataValueField="ProjNumber"
    ValidationGroup="CoReqLine"
    AutoPostBack="true" />

<asp:CustomValidator 
    ID="cvProjects" 
    runat="server" 
    ControlToValidate="ddlProjects" 
    ErrorMessage="some text" 
    Text="some text"
    OnServerValidate="Projects_Validate" 
    ValidateEmptyText="True">
</asp:CustomValidator>

ClassA.ascx.cs

Program don't come to this function

protected void Projects_Validate(object source, ServerValidateEventArgs args)
{
    args.IsValid = false;
}