c# - Foreach 循环错误

Question

我在 foreach 循环中出现指向 in 的错误!？以前从未发生过。这可能是什么原因？我错过了什么吗？

错误信息:

An exception of type 'System.NotSupportedException' occurred in EntityFramework.SqlServer.dll but was not handled in user code

---

Additional information: Unable to create a constant value of type 'System.Object'. Only primitive types or enumeration types are supported in this context.

我的代码:

List<int> WeeksInProject = new List<int>();
var w = from x in db.Activities 
        where x.ProjectID.Equals(1) 
        select x;

foreach (var wNum in w)
{
    WeeksInProject.Add(wNum.WeekNumber);
}

Answer 1

var w = from x in db.Activities 
        where x.ProjectID.Equals(1) select x;

应该是:

var w = from x in db.Activities 
        where x.ProjectID == 1 select x;

如果ProjectID是int?,

var w = from x in db.Activities where 
        x.ProjectID.HasValue &&
        x.ProjectID.Value == 1 select x;