无法创建恒定值。只有原始类型 [英] Unable to create a constant value. Only primitive types

问题描述

dbEntities db = new dbEntities();
foreach (ttCategory c in db.ttCategories)
{
    var tags=(from t in db.ttproduktes where t.ttCategories.Contains(c) select t.ttTags);
    foreach (ttTag t in tags)  // here it says:
                               // Unable to create a constant value - only primitive types
    {
       t.ToString();
    }
}

我究竟做错了什么？

What am i doing wrong?

推荐答案

在LINQ到实体，你不能使用类包含，你只能用原始类型使用它，所以你需要改变这一点：

In linq-to-entities, you can't use Contains with a class, you can only use it with a primitive type, so you need to change this:

where t.ttCategories.Contains(c)

到

 where t.ttCategories.Any(x => x.UniqueProperty == c.UniqueProperty)

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