如何确定一个类型是否实现了特定的泛型接口类型

您必须检查泛型接口的构造类型。

你必须这样做:

foo is IBar<String>

因为IBar<String>表示构造的类型。你必须这样做的原因是，如果你的检查中T是未定义的，编译器不知道你是指IBar<Int32>还是IBar<SomethingElse>。

你必须遍历继承树并找到树中每个类的所有接口，并将typeof(IBar<>)与调用Type.GetGenericTypeDefinition 如果的结果进行比较。当然，这一切都有点痛苦。

更多信息和代码请参见这个答案和这些的。

public interface IFoo<T> : IBar<T> {}
public class Foo : IFoo<Foo> {}


var implementedInterfaces = typeof( Foo ).GetInterfaces();
foreach( var interfaceType in implementedInterfaces ) {
if ( false == interfaceType.IsGeneric ) { continue; }
var genericType = interfaceType.GetGenericTypeDefinition();
if ( genericType == typeof( IFoo<> ) ) {
// do something !
break;
}
}

首先，public class Foo : IFoo<T> {}不能编译，因为你需要指定一个类而不是T，但假设你做了类似public class Foo : IFoo<SomeClass> {}的事情

如果你这样做了

Foo f = new Foo();
IBar<SomeClass> b = f as IBar<SomeClass>;


if(b != null)  //derives from IBar<>
Blabla();

通过使用tck的答案，也可以用以下LINQ查询完成:

bool isBar = foo.GetType().GetInterfaces().Any(x =>
x.IsGenericType &&
x.GetGenericTypeDefinition() == typeof(IBar<>));

作为辅助方法扩展

public static bool Implements<I>(this Type type, I @interface) where I : class
{
if(((@interface as Type)==null) || !(@interface as Type).IsInterface)
throw new ArgumentException("Only interfaces can be 'implemented'.");


return (@interface as Type).IsAssignableFrom(type);
}

使用示例:

var testObject = new Dictionary<int, object>();
result = testObject.GetType().Implements(typeof(IDictionary<int, object>)); // true!

我使用一个稍微简单的版本的@GenericProgrammers扩展方法:

public static bool Implements<TInterface>(this Type type) where TInterface : class {
var interfaceType = typeof(TInterface);


if (!interfaceType.IsInterface)
throw new InvalidOperationException("Only interfaces can be implemented.");


return (interfaceType.IsAssignableFrom(type));
}

用法:

    if (!featureType.Implements<IFeature>())
throw new InvalidCastException();

以下内容应该没有任何问题:

bool implementsGeneric = (anObject.Implements("IBar`1") != null);

如果您想为IBar查询提供一个特定的泛型类型参数，您可以捕获AmbiguousMatchException。

要完全处理类型系统，我认为你需要处理递归，例如IList<T>: ICollection<T>: IEnumerable<T>，没有它你不会知道IList<int>最终实现了IEnumerable<>。

    /// <summary>Determines whether a type, like IList&lt;int&gt;, implements an open generic interface, like
/// IEnumerable&lt;&gt;. Note that this only checks against *interfaces*.</summary>
/// <param name="candidateType">The type to check.</param>
/// <param name="openGenericInterfaceType">The open generic type which it may impelement</param>
/// <returns>Whether the candidate type implements the open interface.</returns>
public static bool ImplementsOpenGenericInterface(this Type candidateType, Type openGenericInterfaceType)
{
Contract.Requires(candidateType != null);
Contract.Requires(openGenericInterfaceType != null);


return
candidateType.Equals(openGenericInterfaceType) ||
(candidateType.IsGenericType && candidateType.GetGenericTypeDefinition().Equals(openGenericInterfaceType)) ||
candidateType.GetInterfaces().Any(i => i.IsGenericType && i.ImplementsOpenGenericInterface(openGenericInterfaceType));


}

如果你想要一个支持泛型基类型和接口的扩展方法，我扩展了sduplooy的答案:

    public static bool InheritsFrom(this Type t1, Type t2)
{
if (null == t1 || null == t2)
return false;


if (null != t1.BaseType &&
t1.BaseType.IsGenericType &&
t1.BaseType.GetGenericTypeDefinition() == t2)
{
return true;
}


if (InheritsFrom(t1.BaseType, t2))
return true;


return
(t2.IsAssignableFrom(t1) && t1 != t2)
||
t1.GetInterfaces().Any(x =>
x.IsGenericType &&
x.GetGenericTypeDefinition() == t2);
}

方法检查类型是否继承或实现泛型类型:

   public static bool IsTheGenericType(this Type candidateType, Type genericType)
{
return
candidateType != null && genericType != null &&
(candidateType.IsGenericType && candidateType.GetGenericTypeDefinition() == genericType ||
candidateType.GetInterfaces().Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == genericType) ||
candidateType.BaseType != null && candidateType.BaseType.IsTheGenericType(genericType));
}

试试下面的扩展。

public static bool Implements(this Type @this, Type @interface)
{
if (@this == null || @interface == null) return false;
return @interface.GenericTypeArguments.Length>0
? @interface.IsAssignableFrom(@this)
: @this.GetInterfaces().Any(c => c.Name == @interface.Name);
}

为了测试它。创建

public interface IFoo { }
public interface IFoo<T> : IFoo { }
public interface IFoo<T, M> : IFoo<T> { }
public class Foo : IFoo { }
public class Foo<T> : IFoo { }
public class Foo<T, M> : IFoo<T> { }
public class FooInt : IFoo<int> { }
public class FooStringInt : IFoo<string, int> { }
public class Foo2 : Foo { }

以及测试方法

public void Test()
{
Console.WriteLine(typeof(Foo).Implements(typeof(IFoo)));
Console.WriteLine(typeof(FooInt).Implements(typeof(IFoo)));
Console.WriteLine(typeof(FooInt).Implements(typeof(IFoo<>)));
Console.WriteLine(typeof(FooInt).Implements(typeof(IFoo<int>)));
Console.WriteLine(typeof(FooInt).Implements(typeof(IFoo<string>)));
Console.WriteLine(typeof(FooInt).Implements(typeof(IFoo<,>)));
Console.WriteLine(typeof(FooStringInt).Implements(typeof(IFoo<,>)));
Console.WriteLine(typeof(FooStringInt).Implements(typeof(IFoo<string,int>)));
Console.WriteLine(typeof(Foo<int,string>).Implements(typeof(IFoo<string>)));
}

var genericType = typeof(ITest<>);
Console.WriteLine(typeof(Test).GetInterfaces().Any(x => x.GetGenericTypeDefinition().Equals(genericType))); // prints: "True"


interface ITest<T> { };


class Test : ITest<string> { }

这对我很管用。