Question

我得到一个奇怪的例外："Unknown Expression type: IIF(e.Accredited.Value, 1, 0)" 运行以下语句：

var x = from e in _EntityManager.TrainingCourses
            select new { Disabled = (e.Accredited.Value ? 1 : 0) };

请帮忙!!如何评估选择

中的（bool？）

由于

Answer 1

此代码是否回答了您的问题？明确地检查bool值似乎可以解决问题：

void Main()
{

    var a = new List<acc>() { 
        new acc(){Accredited = false}, 
        new acc(){Accredited = true}, 
        new acc(){Accredited = null}
        };

    var x = from e in a
        select new { Disabled = (e.Accredited == true ? 1 : 0) };

    foreach (var i in x)
    {
        Console.WriteLine(i);
    }
}
public struct acc
    {
       public bool? Accredited;
    }

输出： 0 1 0

Answer 2

假设e.Accredited是Nullable<bool>（bool?），请尝试以下操作：

var x = from e in _EntityManager.TrainingCourses
        select new { Disabled = (e.Accredited.HasValue && e.Accredited.Value) };

Linq在select子句中评估Nullable类型

2 个答案: