Entity.Contains(AttributeName) 适用于所有注释字段但不适用于注释文本

Question

在下面的代码片段中，我正在检索与订单相关的注释。仅当 notetext 确实包含数据时它才能正常工作。现在，在调试时我发现，在其他情况下它会抛出 Object reference not set to an instance of an object.

异常

我认为以下片段看起来不错，但不确定缺少什么，有解决问题的想法吗？

private void fetchDocument(IOrganizationService service, Guid vOrderId) 
{
    EntityCollection results = null;
    string tempNote = string.Empty;
    string tempFileName = string.Empty;

    ColumnSet cols = new ColumnSet("subject", "filename", "documentbody", "mimetype","notetext");
    QueryExpression query = new QueryExpression {
            EntityName = "annotation" ,
            ColumnSet = cols,
            Criteria = new FilterExpression
            {
                Conditions = {
                new ConditionExpression("objectid",ConditionOperator.Equal,vOrderId)
            }
            }
            };
    results = service.RetrieveMultiple(query);
    Entity defaultRecord = results.Entities.ElementAtOrDefault(0);

    if(defaultRecord.Contains("notetext"))
    {
        tempNote = defaultRecord.GetAttributeValue<string>("notetext");
    }

    if (defaultRecord.Contains("filename"))
    {
        tempFileName = defaultRecord.GetAttributeValue<string>("filename");
    }       
}

Answer 1

你的问题实际上是在这一行：

Entity defaultRecord = results.Entities.ElementAtOrDefault(0);

没有找到结果，意思是

there is no Annotation that exists with an objectid of "vOrderId", or the user that is performing the query, doesn't have rights to read that record.

无论如何，您应该检查 defaultRecord 是否为空，如果是则退出。

这种 null 检查很常见，这就是我编写此 ExtensionMethod 的原因：

public Entity GetFirstOrDefault(this IOrganizationService service, QueryBase qb) {
    return service.RetrieveMultiple(qb)?.Entities.FirstOrDefault();
}

这会将您的代码简化为：

private void fetchDocument(IOrganizationService service, Guid vOrderId) 
{
    EntityCollection results = null;
    string tempNote = string.Empty;
    string tempFileName = string.Empty;

    ColumnSet cols = new ColumnSet("subject", "filename", "documentbody", "mimetype","notetext");
    QueryExpression query = new QueryExpression {
            EntityName = "annotation" ,
            ColumnSet = cols,
            Criteria = new FilterExpression
            {
                Conditions = {
                new ConditionExpression("objectid",ConditionOperator.Equal,vOrderId)
            }
            }
            };

    var defaultRecord = service.GetFirstOrDefault(query);
    if(defaultRecord != null)
    {
        if(defaultRecord.Contains("notetext"))
        {
             tempNote = defaultRecord.GetAttributeValue<string>("notetext");
        }

        if (defaultRecord.Contains("filename"))
        {
            tempFileName = defaultRecord.GetAttributeValue<string>("filename");
        } 
    }
}

Answer 2

你没有防范defaultrecord null。

results = service.RetrieveMultiple(query);
if (results.Entities == null || !results.Entities.Any()) return;
Entity defaultRecord = results.Entities.ElementAt(0);

将答案扩展到备份 result.Entities == null 检查。

检索多个 EntityCollection 并非万无一失。

EntityCollection 属性:

反编译SDK获取多核：

  protected internal virtual EntityCollection RetrieveMultipleCore(QueryBase query)
    {
      bool? retry = new bool?();
      do
      {
        bool forceClose = false;
        try
        {
          using (new OrganizationServiceContextInitializer(this))
            return this.ServiceChannel.Channel.RetrieveMultiple(query);
        }
        catch (MessageSecurityException ex)
        {
          ..
        }
        finally
        {
          this.CloseChannel(forceClose);
        }
      }
      while (retry.HasValue && retry.Value);
      return (EntityCollection) null;
    }

已反编译 SDK 缓存组织服务上下文检索多个：

public override EntityCollection RetrieveMultiple(QueryBase query)
{
   RetrieveMultipleRequest retrieveMultipleRequest = new      RetrieveMultipleRequest();
   retrieveMultipleRequest.Query = query;
   RetrieveMultipleResponse multipleResponse = this.Execute<RetrieveMultipleResponse>((OrganizationRequest) retrieveMultipleRequest);
   if (multipleResponse == null)
     return (EntityCollection) null;
   else
     return multipleResponse.EntityCollection;
}


public EntityCollection EntityCollection
{
   get
   {
     if (this.Results.Contains("EntityCollection"))
        return (EntityCollection) this.Results["EntityCollection"];
     else
        return (EntityCollection) null;
   }
}

Entity.Contains(AttributeName) 适用于所有注释字段但不适用于注释文本

Entity.Contains(AttributeName) works for all annotation fields but not working for notetext

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