插件开发

业务需求 需要在单据保存时执行sql语句 总是报错 请各位大神改下
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Kingdee.BOS;
using Kingdee.BOS.Core.Bill.PlugIn;
using Kingdee.BOS.Core.DynamicForm;
using Kingdee.BOS.Core.DynamicForm.PlugIn.Args;
using Kingdee.BOS.Orm.DataEntity;
using Kingdee.BOS.Core.SqlBuilder;
using Kingdee.BOS.Core.Metadata;
using Kingdee.BOS.Contracts;
using Kingdee.BOS.ServiceHelper;
using Kingdee.BOS.App;
using Kingdee.BOS.DataEntity;

namespace ClassLibrary3
{
public class Class1 : AbstractBillPlugIn
{

public override void AfterDoOperation(AfterDoOperationEventArgs e)
{
base.AfterDoOperation(e);
if (e.Operation.Operation == "Save")
{
Sql = "";//需要执行的语句
int r = DBServiceHelper.Execute(this.Context, sql);
}
}
}
}