c# - 在一个查询中加载关联实体

Question

我有以下有效代码，但我相信它执行多次查找只是为了获取与我的自定义“项目”实体关联的“帐户”实体。

是否可以指定您想要填充哪些关联实体，而不必循环遍历初始结果集？

    public IList<new_project> GetAssociatedProjectsByPostcode(string postcode)
    {
        FilterExpression filter = new FilterExpression();
        filter.FilterOperator = LogicalOperator.And;
        filter.AddCondition(new ConditionExpression("new_project_zippostalcode", ConditionOperator.Equal, postcode));

        QueryExpression query = new QueryExpression();
        query.EntityName = new_project.EntityLogicalName;
        query.ColumnSet = new ColumnSet(true);
        query.Criteria = filter;

        OrganizationServiceCache serviceCache = new OrganizationServiceCache(MemoryCache.Default, base.CrmConnection);

        using (CachedOrganizationService service = new CachedOrganizationService(CrmConnection, serviceCache))
        using (XrmServiceContext xrmServiceContext = new XrmServiceContext(service))
        {
             //Run the query to return the project entities in a list
             IList<new_project> projects = service.RetrieveMultiple(query)
                                            .Entities
                                            .Select(item => item.ToEntity<new_project>())
                                            .ToList<new_project>();

             //Define the relationships we want populated
             Relationship accountRel = new Relationship("new_account_new_project");

             //We cannot call load property with tracking turned on 
             xrmServiceContext.MergeOption = MergeOption.NoTracking;

             //Loop through the original list and get our associations
             foreach (new_project np in projects)
                 xrmServiceContext.LoadProperty(np, accountRel);

             return projects;
        }            
    }

是否可以使用 ServiceContext 生成等效项？

Select Project.Name, Account.Name
From Project
Join Account ON Account.Id = Project.AccountId

编辑:

使用下面 James 描述的链接实体后，我现在得到了以下内容，它生成一个实体集合，其中包含在一个查询中填充的项目和帐户，但我无法将此平面数据集传输到分层对象结构中。

        public IList<new_project> GetAssociatedProjectsByPostcode(string postcode)
    {
        FilterExpression filter = new FilterExpression();
        filter.FilterOperator = LogicalOperator.And;
        filter.AddCondition(new ConditionExpression("new_project_zippostalcode", ConditionOperator.BeginsWith, PostcodeUtility.RegionFromPostcode(postcode)));

        QueryExpression query = new QueryExpression();
        query.EntityName = new_project.EntityLogicalName;
        query.ColumnSet = new ColumnSet(true);
        query.Criteria = filter;

        query.LinkEntities.Add(new LinkEntity(new_project.EntityLogicalName, Account.EntityLogicalName, "new_associatedaccountid", "accountid", JoinOperator.Inner));
        query.LinkEntities[0].Columns = new ColumnSet(true);
        query.LinkEntities[0].EntityAlias = Account.EntityLogicalName;

        OrganizationServiceCache serviceCache = new OrganizationServiceCache(MemoryCache.Default, base.CrmConnection);

        using (CachedOrganizationService service = new CachedOrganizationService(CrmConnection, serviceCache))
        using (XrmServiceContext xrmServiceContext = new XrmServiceContext(service))
        {
            EntityCollection ec = service.RetrieveMultiple(query);

            //*****************************************************************
            //The entity collection is now populated with the accounts but they
            //are just additional key value pairs
            //e.g. (String)((AliasedValue)ec[0]["account.name"]).Value;
            //*****************************************************************

            //Turn the entity collection into our class structure
            IList<new_project> projects = ec.Entities
                                           .Select(item => item.ToEntity<new_project>())
                                           .ToList<new_project>();
            return projects;
        }
    }

Answer 1

是的，这应该非常简单，您有几个选择。

1. FetchXml，这是一种 xml 语法，与 tsql 的方法类似，它不具备所有功能，但您可以与 link-entity 进行连接，如下所示 MSDN .

2. QueryExpression，有一个 LinkEntities 属性，可以像这样使用 MSDN 。

3. 您可以发出 RetrieveRequest，填充 RelatedEntitiesQuery，如图 here 。

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编辑

因此，实体集合看起来返回了我期望的结果(例如，这些帐户的帐户和值) - 我认为 typeof(ec[0]) 是实体？

所以这只是向早期边界的转换，这是错误的。

我没有太多使用 linq to crm，所以我开始猜测，但是从这个 example 来看.

您可能只需要:

1. 在您的服务上启用ProxyTypes，显然这是完整早期绑定(bind)支持所必需的。
2. 将实体转换为您的早期绑定(bind)类型。

例如(来自示例):

_serviceProxy.EnableProxyTypes();

Account retrievedAccount = (Account)_serviceProxy.Retrieve("account", _accountId, cols);

retrievedAccount.Address1_PostalCode = "98052";

Retrieve 仅返回一个实体(EntityCollection.Entities 的类型)，并且转换似乎可以在这里工作。