.net 塞西尔：尝试/最终？

对实现try/catch-in有很好的概述，但他在没有完成完整的try/catch/finally之前就停了下来。那么，如何使用Mono.Cecil实现try/finally呢？

下面是如何注入finally

首先，您需要修复返回语句。你只想要一个

Instruction FixReturns()
{
    if (Method.ReturnType == TypeSystem.Void)
    {
        var instructions = body.Instructions;
        var lastRet = Instruction.Create(OpCodes.Ret);
        instructions.Add(lastRet);

        for (var index = 0; index < instructions.Count - 1; index++)
        {
            var instruction = instructions[index];
            if (instruction.OpCode == OpCodes.Ret)
            {
                instructions[index] = Instruction.Create(OpCodes.Leave, lastRet);
            }
        }
        return lastRet;
    }
    else
    {
        var instructions = body.Instructions;
        var returnVariable = new VariableDefinition("methodTimerReturn", Method.ReturnType);
        body.Variables.Add(returnVariable);
        var lastLd = Instruction.Create(OpCodes.Ldloc, returnVariable);
        instructions.Add(lastLd);
        instructions.Add(Instruction.Create(OpCodes.Ret));

        for (var index = 0; index < instructions.Count - 2; index++)
        {
            var instruction = instructions[index];
            if (instruction.OpCode == OpCodes.Ret)
            {
                instructions[index] = Instruction.Create(OpCodes.Leave, lastLd);
                instructions.Insert(index, Instruction.Create(OpCodes.Stloc, returnVariable));
                index++;
            }
        }
        return lastLd;
    }
}

然后把它缝在一起

void InnerProcess()
{
    body = Method.Body;
    body.SimplifyMacros();
    ilProcessor = body.GetILProcessor();

    var returnInstruction = FixReturns();

    var firstInstruction = FirstInstructionSkipCtor();

    var beforeReturn = Instruction.Create(OpCodes.Nop);
    ilProcessor.InsertBefore(returnInstruction, beforeReturn);

    InjectIlForFinaly(returnInstruction);

    var handler = new ExceptionHandler(ExceptionHandlerType.Finally)
        {
            TryStart = firstInstruction,
            TryEnd = beforeReturn,
            HandlerStart = beforeReturn,
            HandlerEnd = returnInstruction,
        };

    body.ExceptionHandlers.Add(handler);
    body.InitLocals = true;
    body.OptimizeMacros();
}

---

发现检查过的示例内容丰富且有用。但是，在更复杂的条件下，确实遇到了问题。在FixReturns（）中，无论是void还是non-void返回作用域，通过创建新指令来更改ret->leave的方法都会删除原始指令。这可能会将其他指令作为操作数留给孤立指令（例如，分支到原始ret）。结果代码最终无效

我们只是简单地更新了现有ret指令的操作码/操作数对，而不是创建新的操作码/操作数对，所有这些看起来都很好

---

干杯。

所以这基本上与那篇文章中描述的过程相同，只是将ExceptionHandlerType.Finally传递到新的ExceptionHandler（）。如果您想要try/catch/finally，您将创建两个“ExceptionHandler”实例并将它们添加到方法中，一个用于catch，一个用于finally。如果是这种情况，那么名称肯定会令人困惑，因为您并没有真正创建新的异常处理程序，至少对于“finally”。谢谢你的指点。

void InnerProcess()
{
    body = Method.Body;
    body.SimplifyMacros();
    ilProcessor = body.GetILProcessor();

    var returnInstruction = FixReturns();

    var firstInstruction = FirstInstructionSkipCtor();

    var beforeReturn = Instruction.Create(OpCodes.Nop);
    ilProcessor.InsertBefore(returnInstruction, beforeReturn);

    InjectIlForFinaly(returnInstruction);

    var handler = new ExceptionHandler(ExceptionHandlerType.Finally)
        {
            TryStart = firstInstruction,
            TryEnd = beforeReturn,
            HandlerStart = beforeReturn,
            HandlerEnd = returnInstruction,
        };

    body.ExceptionHandlers.Add(handler);
    body.InitLocals = true;
    body.OptimizeMacros();
}