PredicateBuilder与LINQ

Question

我试图提取(从AsyncOperationBase表中)运行的工作流的所有实例，这些实例都有许多谓词。

我知道您不能使用像myArray.Contains(x.WorkflowActivationId.Id)这样的东西，所以我尝试用PredicateBuilder动态地构建一个谓词

到目前为止，我的情况如下：

var predicate = PredicateBuilder.False<Service.AsyncOperation>();

//Apparently, checking for null is suppose to prevent my issue from happening...
predicate = predicate.And(x => x.Name == searchWorkflowDefinitionText.Text);
predicate = predicate.And(x => x.StatusCode != null);
predicate = predicate.And(x => x.StatusCode.Value == 10);
predicate = predicate.And(x => x.WorkflowActivationId != null);


foreach (Guid s in listBox3.Items)
{
    predicate = predicate.Or(x => x.WorkflowActivationId.Id == s);
}


var r = (from c in xrm.CreateQuery<Service.AsyncOperation>().AsExpandable().Where(predicate)
                         select c).ToList();

但是，我最终得到了许多LINQ可怕的例外：

Invalid 'where' condition. An entity member is invoking an invalid property or method.

据我所知，要避免这个错误，您需要“爬行”属性。比如：

predicate = predicate.Or(x => x.WorkflowActivationId == s);

必须更改为

predicate = predicate.Or(x => x.WorkflowActivationId.Id == s);

此外，谓词的左侧必须是一个实体属性。再一次，据我所知，我的谓词满足了这些要求，所以我有点不知所措。

有什么想法吗？

Answer 1

我想我需要绕过LINQ的限制，做这2部分。

第一次：

var t = xrm.AsyncOperationSet.Where(x => x.StatusCode.Value == 10 && x.Name == wkname).Select(y => new Service.AsyncOperation
                {
                    AsyncOperationId = y.AsyncOperationId.Value,
                    WorkflowActivationId = y.WorkflowActivationId
                }).ToList();

我现在真的只需要这两个属性。

这样我就可以完全访问t的内容了。

var y = t.Where(x => myArray.Contains(x.WorkflowActivationId.Id)).ToList();