Question

如何使用反射来获取泛型类型的属性的名称和声明类。如果我读到一个迄今为止没有写过任何内容的属性，目的是获得异常。其中一个问题是检查必须独立于声明类。

value.GetType().DeclaringType始终为null。

using System;

namespace TestCodeContract
{

    public struct CheckForNull<T> where T : struct
    {
        private T? backingField;

        public static implicit operator T(CheckForNull<T> value)
        {
            if (!(value.backingField.HasValue))
            {
                var t1 = value.GetType().DeclaringType; // always null.

                var propertyName = "Delta"; // TODO get from Reflection
                var className = "ContractClass"; // TODO get from Reflection
                var msg = String.Format("Proprety '{0}' in class '{1}' is not initialized", propertyName, className);
                throw new ApplicationException(msg);
            }
            return value.backingField.Value;
        }

        public static implicit operator CheckForNull<T>(T value)
        {
            return new CheckForNull<T> { backingField = value };
        }
    }

    public class ContractClass
    {
        public CheckForNull<int> Delta { get; set; }

        public void Test1()
        {
            int x = Delta; // Wanted: "Property 'Delta' in class 'ContractClass' is not initialized"
        }
    }
}

Answer 1

不，你不能这样做。我会建议这样的事情：

// You could do this without the constraint, with a bit of extra work.
public class ReadOnlyAfterWrite<T> where T : struct
{
    private T? value;
    private readonly string property;
    private readonly string type;

    public ReadOnlyAfterWrite(string property, string type)
    {
        this.property = property;
        this.type = type;
    }

    public T Value
    {
        get
        {
            if (value == null)
            {
                // Use type and property here
                throw new InvalidOperationException(...);
            }
            return (T) value;
        }
        set { this.value = value; }
    }
}

public class ContractClass
{
    // This is what I'd do in C# 6. Before that, probably just use string literals.
    private readonly ReadOnlyAfterWrite<int> delta =
        new ReadOnlyAfterWrite(nameof(Delta), nameof(ContractClass));

    public int Delta
    {
        get { return delta.Value; }
        set { delta.Value = value; }
    }
}

虽然它在实施中并非非常干净，但我认为它是一个更好的公共API - 它被保护的事实对于来电者来说是看不见的看到int属性。

获取属性的名称并声明类

1 个答案: