C# 反射呼叫擴充類方法

小紫蘇 發表於 2022-01-21
C#

今天封裝Protobuf封包時候遇到一個問題;

Protobuf的反序列化方法MergeFrom,是寫在擴充套件類裡的;c#擴充類

通過反射獲取不到這個方法,就沒法使用Type來泛型封裝...

然而仔細一想,擴充類不也是類嗎,直接反射獲取擴充類方法好了;

在看Google.Protobuf原始碼,找到這個類;

image-20220121155555518

這個MergeFrom方法就是需要的;

那這個IMessage介面怎麼辦;

所有自動生成的protobuf類都只自動繼承兩個介面;

image-20220121160317050

所以傳需要序列化的類即可;

//接收到伺服器訊息;反序列化後執行相應路由方法
public void DispatchProto(int protoId, byte[] bytes)
{
    if (!ProtoDic.ContainProtoId(protoId))
    {
        Logger.LogError($"Unkown ProtoId:{protoId}");
        return;
    }       
    Type protoType = ProtoDic.GetProtoTypeByProtoId(protoId);
    Logger.Log($"protoId:{protoId};--typeName:{protoType.FullName}");

    //列印傳輸獲得的位元組的utf-8編碼
    PrintUTF8Code(bytes);

    Type tp = typeof(Google.Protobuf.MessageExtensions);
	
    //反射獲取擴充類方法MergeFrom
	MethodInfo method = ReflectTool.GetExtentMethod(tp,"MergeFrom", protoType, typeof(byte[]));

    //反射建立例項,回撥方法
    object obj = ReflectTool.CreateInstance(protoType);
    ReflectTool.MethodInvoke(method, obj, obj, bytes);

    sEvents.Enqueue(new KeyValuePair<Type, object>(protoType, obj));
}

ProtoDic儲存了protoId和對應的型別Type;

ReflectTool.GetExtentMethod——封裝了GetMethod方法,為了能連續傳入多個引數,而不是傳Type陣列;

ReflectTool.MethodInvoke——和上面目的一樣;

//獲取擴充套件方法
public static MethodInfo GetExtentMethod(Type extentType, string methodName, params Type[] funcParams)
{
    MethodInfo method = GetMethod(extentType, methodName, funcParams);
    return method;
}

public static object MethodInvoke(MethodInfo method, object obj, params object[] parameters)
{
    return method.Invoke(obj, parameters);
}
//通過Type建立例項,返回Object
public static object CreateInstance(Type refType, params object[] objInitial) 
{
    object res = System.Activator.CreateInstance(refType, objInitial);

    if (res == null)
    {
        Logger.LogError($"Reflect create Type:{refType.FullName} is null");
    }

    return res;
}

最後寫測試程式碼:

pb.BroadCast結構為:

message BroadCast{
    int32 PID =1;
    int32 Tp = 2;
    string Content = 3;        
}

執行程式碼:

Pb.BroadCast bo = new Pb.BroadCast();
bo.PID = 1;
bo.Tp = 1;
bo.Content = "Perilla";
byte[] res = bo.ToByteArray();

//列印位元組的utf-8編碼
StringBuilder strBuilder = new StringBuilder();
for (int i = 0; i < res.Length; ++i)
{
    strBuilder.Append(res[i]);
    strBuilder.Append('-');
}

Logger.Log(strBuilder.ToString());
Pb.BroadCast bo2 = new Pb.BroadCast();
bo2.MergeFrom(res);
Logger.LogFormat("{0}=={1}=={2}", bo2.PID, bo2.Tp, bo2.Content);

執行結果:

image-20220121162356185