.net - 属性参数必须是一个常量表达式

Question

以下问题是否有任何解决方法？

An attribute argument must be a constant expression

我想在属性的参数中使用小数。

Answer 1

不幸的是，您不能在属性值中使用小数，因为CLR本身并不真正了解System.Decimal类型-它不是像int，double等原始类型。C#编译器基本上将其伪装为小数类型的const字段，但是使用属性无法达到相同的效果。

根据C#3规范的17.1.3节:

The types of positional and named parameters for an attribute class are limited to the attribute parameter types, which are:

• One of the following types: bool, byte, char, double, float, int, long, sbyte, short, string, uint, ulong, ushort.
• The type object.
• The type System.Type.
• An enum type, provided it has public accessibility and the types in which it is nested (if any) also have public accessibility (§17.2).
• Single-dimensional arrays of the above types.

然后在第17.2节中:

An expression E is an attribute-argument-expression if all of the following statements are > true:

• The type of E is an attribute parameter type (§17.1.3).
• At compile-time, the value of E can be resolved to one of the following:
  • A constant value.
  • A System.Type object.
  • A one-dimensional array of attribute-argument-expressions.