Question

我正在使用C＃/ .NET 4.0和一个提供以下功能的Protocol Buffers库（protobuf-net）。

public static class Serializer {
    public static void Serialize<T>(Stream destination, T instance);
    public static void Serialize<T>(SerializationInfo info, T instance);
    public static void Serialize<T>(XmlWriter writer, T instance);
    public static void Serialize<T>(SerializationInfo info, StreamingContext context, T instance);
    public static T Deserialize<T>(Stream source);
}

我需要使用非通用等价物包装其中两个调用。具体来说，我想要

void SerializeReflection(Stream destination, object instance);
object DeserializeReflection(Stream source, Type type);

只是在运行时调用Serializer的相应通用成员。 我已使用DeserializeReflection方法处理以下代码：

public static object DeserializeReflection(Stream stream, Type type)
{
    return typeof(Serializer)
        .GetMethod("Deserialize")
        .MakeGenericMethod(type)
        .Invoke(null, new object[] { stream });
}

SerializeReflection方法正在给我带来麻烦。我刚开始尝试以下代码：

public static void SerializeReflection(Stream stream, object instance)
{
    typeof(Serializer)
        .GetMethod("Serialize")
        .MakeGenericMethod(instance.GetType())
        .Invoke(null, new object[] { stream, instance });
}

问题是typeof(Serializer)和.Invoke(...)之间的部分无效。拨打GetMethod("Serialize")的电话会给我AmbiguousMatchException，因为有四种方法名为“Serialize。”

然后我尝试使用GetMethod的重载来获取System.Type数组来解析绑定：

GetMethod("Serialize", new[] { typeof(Stream), instance.GetType() })

但这只是GetMethod null的结果。

如何使用反射获取MethodInfo的{{1}}，其中void Serializer.Serialize<T>(Stream, T)为T？

Answer 1

尝试使用下一个代码段，看看它是否符合您的需求。它创建方法public static void Serialize<T>(Stream destination, T instance)的密切类型实例。在这种情况下，它选择第一个方法Stream作为参数，但您可以将此谓词method.GetParameters().Any(par => par.ParameterType == typeof(Stream))更改为您想要的任何内容

public static object DeserializeReflection(Stream stream, object instance)
{
   return typeof(Serializer)
        .GetMethods()
        .First(method => method.Name == "Serialize" && method.GetParameters().Any(par => par.ParameterType == typeof(Stream)))
        .MakeGenericMethod(instance.GetType())
        .Invoke(null, new object[] { stream, instance });
}

Answer 2

对于这类事情，我经常使用像这样的辅助方法

public static MethodInfo MakeGenericMethod<TSourceType>(Type genericArgument, string methodName, Type[] parameterTypes, params int[] indexesWhereParameterIsTheGenericArgument)
{
    //Get the type of the thing we're looking for the method on
    var sourceType = typeof (TSourceType);
    //Get all the methods that match the default binding flags
    var allMethods = sourceType.GetMethods();
    //Get all the methods with the same names
    var candidates = allMethods.Where(x => x.Name == methodName);

    //Find the appropriate method from the set of candidates
    foreach (var candidate in candidates)
    {
        //Look for methods with the same number of parameters and same types 
        //   of parameters (excepting for ones that have been marked as 
        //   replaceable by the generic parameter)
        var parameters = candidate.GetParameters();
        var successfulMatch = parameters.Length == parameterTypes.Length;

        if (successfulMatch)
        {
            for (var i = 0; i < parameters.Length; ++i)
            {
                successfulMatch &= parameterTypes[i] == parameters[i].ParameterType || indexesWhereParameterIsTheGenericArgument.Contains(i);
            }
        }

        //If all the parameters were validated, make the generic method and return it
        if (successfulMatch)
        {
            return candidate.MakeGenericMethod(genericArgument);
        }
    }

    //We couldn't find a suitable candidate, return null
    return null;
}

要使用它，你可以

var serializeMethod = MakeGenericMethod<Serializer>(instance.GetType(), "Serialize", new[]{typeof(stream), typeof(object)}, 1);

使用System.Type调用泛型方法

2 个答案: