使用反射动态地将属性转换为其实际类型

Question

我需要动态地将属性转换为其实际类型.我如何/可以使用反射做到这一点？

解释我正在努力的真实场景.我试图在Entity Framework属性上调用"First"扩展方法.要在Framework上下文对象上调用的特定属性作为字符串传递给方法(以及要检索的记录的id).所以我需要对象的实际类型才能调用First方法.

我不能在对象上使用"Where"方法,因为lambda或delegate方法仍然需要对象的实际类型才能访问属性.

此外,由于对象是由实体框架生成的,因此我无法将类型转换为接口并对其进行操作.

这是场景代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Reflection;

namespace NmSpc
{

    public class ClassA
    {
        public int IntProperty { get; set; }
    }

    public class ClassB
    {
        public ClassA MyProperty { get; set; }
    }

    public class ClassC
    {
        static void Main(string[] args)
        {
            ClassB tester = new ClassB();

            PropertyInfo propInfo = typeof(ClassB).GetProperty("MyProperty");
            //get a type unsafe reference to ClassB`s property
            Object property = propInfo.GetValue(tester, null);

            //get the type safe reference to the property
            ClassA typeSafeProperty = property as ClassA;

            //I need to cast the property to its actual type dynamically. How do I/Can I do this using reflection?
            //I will not know that "property" is of ClassA apart from at runtime
        }
    }
}

Answer 1

public object CastPropertyValue(PropertyInfo property, string value) { 
if (property == null || String.IsNullOrEmpty(value))
    return null;
if (property.PropertyType.IsEnum)
{
    Type enumType = property.PropertyType;
    if (Enum.IsDefined(enumType, value))
        return Enum.Parse(enumType, value);
}
if (property.PropertyType == typeof(bool))
    return value == "1" || value == "true" || value == "on" || value == "checked";
else if (property.PropertyType == typeof(Uri))
    return new Uri(Convert.ToString(value));
else
    return Convert.ChangeType(value, property.PropertyType);  }

Answer 2

我有一些时间,所以我尝试使用VS2010来解决我的问题,我认为我之前是正确的,但我认为动态关键字会"解决"我的问题.请参阅下面的代码.

using System.Reflection;

namespace TempTest
{
    public class ClassA
    {
        public int IntProperty { get; set; }
    }

    public class ClassB
    {
        public ClassB()
        {
            MyProperty = new ClassA { IntProperty = 4 };
        }
        public ClassA MyProperty { get; set; }
    }

    public class Program
    {
        static void Main(string[] args)
        {
            ClassB tester = new ClassB();

            PropertyInfo propInfo = typeof(ClassB).GetProperty("MyProperty");
            //get a type unsafe reference to ClassB`s property
            dynamic property = propInfo.GetValue(tester, null);

            //casted the property to its actual type dynamically
            int result = property.IntProperty; 
        }
    }
}

Answer 3

获得反射类型后，您可以使用Convert.ChangeType().