Register the component libraries

<%@ Register TagPrefix="DNL" Assembly="DbNetLink.DbNetSuiteVS" Namespace="DbNetLink.DbNetSuiteVS" %>

Server Control

    <DNL:DbNetGrid 
        ID="DbNetGrid1" 
        runat="server" 
        ConnectionString="SamplesDatabaseVistaDB" 
        FromPart="Products Join Suppliers on Products.SupplierID = Suppliers.SupplierID"
        Update="true"
        OnBeforeRecordInsert="ValidateInsert" >
        <Columns>
            <DNL:GridColumn ColumnExpression="Products.ProductName"  Required="true" />
            <DNL:GridColumn ColumnExpression="Suppliers.CompanyName" Required="true" />
            <DNL:GridColumn ColumnExpression="Suppliers.Country" Required="true" />
            <DNL:GridColumn ColumnExpression="Products.UnitPrice" Required="true" Edit="true" />
            <DNL:GridColumn ColumnExpression="Products.SupplierID" Display="false" Required="true" Lookup="select SupplierID, CompanyName from Suppliers" />
            <DNL:GridColumn ColumnExpression="Products.ProductID" Display="false" Edit="false" />
        </Columns>
    </DNL:DbNetGrid>

Server-side script

///////////////////////////////////////////////////////////////
public bool ValidateInsert(object sender, RecordInsertEventArgs eventArgs)
///////////////////////////////////////////////////////////////
{
	ListDictionary Params = new ListDictionary();
	Params["supplierID"] = eventArgs.Record["SupplierID"];

	eventArgs.Database.ExecuteSingletonQuery("select country from suppliers where supplierid = @supplierid", Params);
	
	if ( eventArgs.Database.Reader["country"].ToString() == "France" )
	{
        eventArgs.Message = "We currenntly are not accepting new products from France.";
		return false;
	}
	else
	{
		return true;
	}
}