c# - ILGenerator 捕获异常不起作用

Question

我正在使用 System.Reflection.Emit 为类型生成包装器。在某一时刻，原始对象可能会在访问时抛出错误 (FaultException)，并且该错误应该被我的 try { } catch (Exception e) { } 捕获我已经实现了，但它没有。

代码由 ILSpy 正确显示.

try
{
    if (original.Station != null)
    {
        if (objectDictionary.ContainsKey(original.Station))
        {
            this.Station = (objectDictionary[original.Station] as StationWrapper);
        }
        else
        {
            this.Station = new StationWrapper(original.Station, objectDictionary);
        }
    }
}
catch (Exception arg_6D_0)
{
    ReportManager.Log(arg_6D_0);
}

代码生成

这是程序集生成的代码。

Label ex = il.BeginExceptionBlock();
....
// Exception block end
il.Emit(OpCodes.Leave, ex);
il.BeginCatchBlock(typeof(Exception));
il.Emit(OpCodes.Call, ReportManager_Log);
il.EndExceptionBlock();

编辑

异常被用户代码捕获，而不是被 IL 代码捕获。

反汇编

在这里删除了客户的一些命名空间。写入行是在最后几分钟添加的。

.try
{
    IL_0019: ldarg.1
    IL_001a: call instance class [...]...Station [...]...StationBase::get_Station()
    IL_001f: brfalse IL_0063

    IL_0024: ldarg.2
    IL_0025: ldarg.1
    IL_0026: call instance class [...]...Station [...]...StationBase::get_Station()
    IL_002b: call instance bool class [mscorlib]System.Collections.Generic.Dictionary`2<object, object>::ContainsKey(!0)
    IL_0030: brfalse IL_0051

    IL_0035: ldarg.0
    IL_0036: ldarg.2
    IL_0037: ldarg.1
    IL_0038: call instance class [...]...Station [...]...StationBase::get_Station()
    IL_003d: call instance !1 class [mscorlib]System.Collections.Generic.Dictionary`2<object, object>::get_Item(!0)
    IL_0042: isinst ...StationWrapper
    IL_0047: call instance void ...StationBaseWrapper::set_Station(class ...StationWrapper)
    IL_004c: br IL_0063

    IL_0051: ldarg.0
    IL_0052: ldarg.1
    IL_0053: call instance class [...]...Station [...]...StationBase::get_Station()
    IL_0058: ldarg.2
    IL_0059: newobj instance void ....StationWrapper::.ctor(class [...]...Station, class [mscorlib]System.Collections.Generic.Dictionary`2<object, object>)
    IL_005e: call instance void ...StationBaseWrapper::set_Station(class ...StationWrapper)

    IL_0063: leave IL_007c
} // end .try
catch [mscorlib]System.Exception
{
    IL_0068: ldstr "Its comming home"
    IL_006d: call void [mscorlib]System.Console::WriteLine(string)
    IL_0072: call void [...Report]...ReportManager::Log(class [mscorlib]System.Exception)
    IL_0077: leave IL_007c
} // end handler

编辑2

当在 IL 代码中抛出 System.Exception 时，在 FaultException'1 发生之前，异常会得到处理。使用 Exception 和 ArgumentException 进行测试。

Answer 1

这里一切正常；您确定它不是嵌套的异常 block 吗？

例子:

using System;
using System.Reflection.Emit;

public class Test
{
    static void Main()
    {
        var dm = new DynamicMethod("foo", null, new[] {typeof(bool)});
        var il = dm.GetILGenerator();

        Label ex = il.BeginExceptionBlock();
        il.Emit(OpCodes.Ldarg_0);
        il.EmitCall(OpCodes.Call, typeof(Test).GetMethod("Throw"), null);
        il.Emit(OpCodes.Leave, ex);

        il.BeginCatchBlock(typeof(Exception));
        il.EmitCall(OpCodes.Call, typeof(Test).GetMethod("Log"), null);
        il.EndExceptionBlock();
        il.Emit(OpCodes.Ldstr, "done");
        il.EmitCall(OpCodes.Call, typeof(Console).GetMethod("WriteLine",
                      new[] {typeof(string)}), null);

        il.Emit(OpCodes.Ret);
        var act = (Action<bool>)dm.CreateDelegate(typeof (Action<bool>));
        Console.WriteLine("Expect success:");
        act(false);
        Console.WriteLine("Expect fail:");
        act(true);
        Console.WriteLine("(all done)");
    }
    public static void Throw(bool fatal)
    {
        if(fatal) throw new InvalidOperationException("Boom!");
    }
    public static void Log(Exception ex)
    {
        Console.WriteLine("Error: " + ex.Message);
    }
}