自动生成单据失败，烦请协助

好，如下创建生成单据不能成功，烦请告之是否少了什么代码：

public override void AfterButtonClick(Kingdee.BOS.Core.DynamicForm.PlugIn.Args.AfterButtonClickEventArgs e)
{ //依单据标识，获取单据对象
var bussnessInfo = MetaDataServiceHelper.GetFormMetaData(this.Context, "LT_AutoCreateBill").BusinessInfo;
var billDynamicObjectType = bussnessInfo.GetDynamicObjectType();
//创建一个单据字段动态对象
DynamicObject billobj = new DynamicObject(billDynamicObjectType);
//为字段姓名赋值
bussnessInfo.GetField("FName").DynamicProperty.SetValue(billobj, "A001");
//为类别下拉框赋值
bussnessInfo.GetField("FDZType").DynamicProperty.SetValue(billobj, "CG");
//创建单据体对象
DynamicObjectCollection dyEntitys = billobj["LT_AutoCreateBillEntry"] as DynamicObjectCollection;
DynamicObject dyEntity = null;
//循环单据体赋值
for (int i = 0; i < 3; i++)
{
dyEntity = dyEntitys.DynamicCollectionItemPropertyType.CreateInstance() as DynamicObject;
dyEntity["FMaterialNumber"] = "FFLM" + i.ToString();
dyEntity["FInputDate"] = DateTime.Now.AddDays(i);
dyEntitys.Add(dyEntity);
}
//调用暂存事件
BusinessDataServiceHelper.Draft(this.Context, bussnessInfo, billobj, null, "Draft");
base.AfterButtonClick(e);
}