c# - 如果不支持包含，如何在 LINQ to Entities( Entity Framework )中执行 SQL 样式 'IN' 语句？

Question

我正在使用 LINQ to Entities(不是 LINQ to SQL)，但在创建“IN”样式查询时遇到了问题。这是我目前的查询:

var items = db.InventoryItem
                .Include("Kind")
                .Include("PropertyValues")
                .Include("PropertyValues.KindProperty")
                .Where(itm => valueIds.Contains(itm.ID)).ToList<InventoryItem>();

然而，当我这样做时，会抛出以下异常:

LINQ to Entities does not recognize the method 'Boolean Contains(Int64)' method, and this method cannot be translated into a store expression.

有人对此有解决方法或其他解决方案吗？

Answer 1

你需要使用这个:

.Where(string.Format("it.ID in {0}", string.Join(",", valueIds.ToArray())));

或者动态构造 WHERE 部分，如 this邮政。

附言- 信息已更新，此答案更新如下以保持相关性:

引用的链接包含以下更新:

...in EF4 we added support for the Contains method and at least in this specific case for collection-valued parameters. Therefore this kind of code now works right out of the box and it is not necesary to use any additinal expression building method:

var statusesToFind = new List<int> {1, 2, 3, 4};
var foos = from foo in myEntities.Foos
           where statusesToFind.Contains(foo.Status)
           select foo;