**【应用场景】**
一般的业务单据指定了link实体，如果下推的时候跟link无关，则无法关联。本案例则是先有下游单据，如何跟已有的上游单据进行关联。
**【案例演示】**
``` csharp
<1>编写列表插件，代码如下。
using Kingdee.BOS.Core.DynamicForm.PlugIn;
using Kingdee.BOS.Core.DynamicForm.PlugIn.Args;
using Kingdee.BOS.Orm.DataEntity;
using Kingdee.BOS.Util;
using System;
using System.ComponentModel;
using System.Linq;
namespace Kingdee.BOS.PlugInTest
{
/// <summary>
/// 【服务插件】二开创建关联关系
/// </summary>
[Description("【服务插件】二开创建关联关系"), HotUpdate]
public class CreateLink : AbstractOperationServicePlugIn
{
/// <summary>
/// 执行操作事务前事件（事务外）
/// </summary>
/// <param name="e"></param>
public override void BeforeExecuteOperationTransaction(BeforeExecuteOperationTransaction e)
{
base.BeforeExecuteOperationTransaction(e);
// 没有通过校验的数据，则跳过
if (e.SelectedRows == null || e.SelectedRows.Count() == 0)
return;
var form = this.BusinessInfo.GetForm();
if (form == null)
return;
var linkSets = this.BusinessInfo.GetForm().LinkSet;
if (linkSets == null || linkSets.LinkEntitys == null || linkSets.LinkEntitys.Count == 0)
return;
// 单据关联配置
var linkEntity = linkSets.LinkEntitys[0];
// 关联的单据体实体
var entity = this.BusinessInfo.GetEntity(linkEntity.ParentEntityKey);
// 关联实体
var linkEntry = this.BusinessInfo.GetEntity(linkEntity.Key);
foreach (var data in e.SelectedRows)
{
if (data.DataEntity.Contains(entity.EntryName))
{
DynamicObjectCollection entityDatas = data.DataEntity[entity.EntryName] as DynamicObjectCollection;
if (entityDatas == null || entityDatas.Count == 0)
continue;
foreach (var entityData in entityDatas)
{
if (entityData.DynamicObjectType.Properties.ContainsKey(linkEntity.Key))
{
var linkObj = new DynamicObject(linkEntry.DynamicObjectType);
bool createFlag = false;
DynamicObjectCollection linkDatas = entityData[linkEntity.Key] as DynamicObjectCollection;
if (linkDatas == null || linkDatas.Count == 0)
{
createFlag = true;
}
else
{
// 检查是否有对应的关联关系
var linkData = linkDatas.FirstOrDefault(x =>
"36afc0f8-0baf-4183-a813-0a6f9c7b52b9".EqualsIgnoreCase(x["RuleId"].ToString())
&& "T_PUR_ReqEntry".EqualsIgnoreCase(x["STableName"].ToString())
&& 213784 == Convert.ToInt64(x["SBillId"])
&& 216478 == Convert.ToInt64(
