泛型构造函数和反射

本文介绍了泛型构造函数和反射的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

有可能看到哪个构造函数是通用的吗?

Is it possible to see which constructor was the generic one?

internal class Foo<T> { public Foo( T value ) {} public Foo( string value ) {} } var constructors = typeof( Foo<string> ).GetConstructors();

属性'ContainsGenericParameters'返回两个构造函数均为false的信息.有没有办法发现constructors [0]是通用的?它们都具有相同的签名，但是我想将真实"字符串称为一个.

The property 'ContainsGenericParameters' returns me for both constructors false. Is there any way to find out that constructors[0] is the generic one? They both have the same signature, but I would like to call the "real" string one.

我想使用

ilGen.Emit( OpCodes.Newobj, constructorInfo );

所以我需要使用绑定版本.但我想调用最佳"构造函数.那应该是标准行为.当我打电话

so I need to work with the bound version. But I would like to invoke the "best" constructor. That should be the standard behaviour. When I call

new Foo<string>()

具有字符串签名的构造函数(而不是具有通用签名的构造函数)被调用.我的代码也应该如此.

the constructor with the string-signature (and not the one with the generic signature) is called. The same should happen with my code.

推荐答案

您需要System.Reflection.ParameterInfo.ParameterType.IsGenericParameter.这是通过的VS2008单元测试，它说明了这一点:

You want System.Reflection.ParameterInfo.ParameterType.IsGenericParameter. Here's a VS2008 unit test that passes that illustrates this:

班级:

public class Foo<T> { public Foo(T val) { this.Value = val.ToString(); } public Foo(string val) { this.Value = "--" + val + "--"; } public string Value { get; set; } }

测试方法:

Foo<string> f = new Foo<string>("hello"); Assert.AreEqual("--hello--", f.Value); Foo<int> g = new Foo<int>(10); Assert.AreEqual("10", g.Value); Type t = typeof(Foo<string>); t = t.GetGenericTypeDefinition(); Assert.AreEqual(2, t.GetConstructors().Length); System.Reflection.ConstructorInfo c = t.GetConstructors()[0]; System.Reflection.ParameterInfo[] parms = c.GetParameters(); Assert.AreEqual(1, parms.Length); Assert.IsTrue(parms[0].ParameterType.IsGenericParameter); c = t.GetConstructors()[1]; parms = c.GetParameters(); Assert.AreEqual(1, parms.Length); Assert.IsFalse(parms[0].ParameterType.IsGenericParameter);

这里值得注意的是parms [0] .ParameterType.IsGenericParameter检查，它检查参数是否为通用.

The notable point here is the parms[0].ParameterType.IsGenericParameter check which checks if the parameter is a generic or not.

一旦找到了构造函数，就可以将ConstructorInfo传递给Emit.

Once you've found your constructor then you've got the ConstructorInfo to pass to Emit.

public System.Reflection.ConstructorInfo FindStringConstructor(Type t) { Type t2 = t.GetGenericTypeDefinition(); System.Reflection.ConstructorInfo[] cs = t2.GetConstructors(); for (int i = 0; i < cs.Length; i++) { if (cs[i].GetParameters()[0].ParameterType == typeof(string)) { return t.GetConstructors()[i]; } } return null; }

不确定自己的意图是什么.

Not exactly sure what your intention is though.