将Lambda表达式声明为类常量字段 [英] Declare Lambda Expression as a class constant field

问题描述

为什么不能声明类型为 Lambda Expression 的类常量。我想要这样的东西：

Why isn't it possible to declare a class constant filed of type Lambda Expression. I want Something like this:

class MyClass
{
   public const Expression<Func<string,bool>> MyExpr = (string s) => s=="Hello!";
}

但是我得到了编译错误：表达式不能包含匿名方法或lambda表达式

But I get the compile error: Expression cannot contain anonymous methods or lambda expressions

推荐答案

这只是C＃和CLR的局限性。只有原始数值，字符串文字和<$​​ c $ c> null 可以用作常量字段的值。表达式树表示为对象的普通图，不能显示为常量。

This is just a limitation of C# and CLR. Only primitive numeric values, string literals and null can be used as a value of a constant field. Expression trees are represented as a normal graph of objects and can't appear as a constant value.

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