c# - 属性参数必须是常量表达式，...- 创建数组类型的属性

Question

这是我的自定义属性和我正在使用它的类:

[MethodAttribute(new []{new MethodAttributeMembers(), new MethodAttributeMembers()})]
public class JN_Country
{

}

public class MethodAttribute : Attribute
{
    public MethodAttributeMembers[] MethodAttributeMembers { get; set; }

    public MethodAttribute(MethodAttributeMembers[] methodAttributeMemberses)
    {
        MethodAttributeMembers = methodAttributeMemberses;
    }
}

public class MethodAttributeMembers
{
    public string MethodName { get; set; }
    public string Method { get; set; }
    public string MethodTitle { get; set; }
}

上面第一行显示的语法错误:

An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type

为什么会出现这个错误？

Answer 1

这补充了 Simon 已经提供的信息。

我在这里找到了一些文档:Attribute parameter types :

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 (Attribute specification).
• Single-dimensional arrays of the above types. (emphasis added by me)

A constructor argument or public field which does not have one of these types, cannot be used as a positional or named parameter in an attribute specification.

最后一个要点解释了您的语法错误。您已经定义了一个一维数组，但它应该只是前面要点中列出的原始类型、字符串等。