C# 为什么ILGenerator在Foreach语句中插入LEVE指令

我生成以下代码：

public override void Map(IEnumerable enumerable1)
{
    List<int> list = new List<int>();
    foreach (object obj2 in enumerable1)
    {
    }
}

以下是结果IL（请参见

IL001f

）：

.method公共虚拟实例无效映射（类[mscorlib]System.Collections.IEnumerable A_1）cil托管
{
//代码大小54（0x36）
.maxstack 5
.locals init（类[mscorlib]System.Collections.Generic.List`1 V_0，
对象V_1，
类[mscorlib]System.Collections.IEnumerator V_2，
类[mscorlib]System.IDisposable V_3）
IL_0000:newobj实例无效类[mscorlib]System.Collections.Generic.List`1:：.ctor（）
IL_0005:stloc.0
IL_0006:ldarg.1
IL_0007:callvirt实例类[mscorlib]System.Collections.IEnumerator[mscorlib]System.Collections.IEnumerable:：GetEnumerator（）
IL_000c:stloc.2
尝试
{
IL_000d:br.s IL_0017
IL_000f:ldloc.2
IL_0010:callvirt实例对象[mscorlib]System.Collections.IEnumerator:：get_Current（）
IL_0015:stloc.1
IL_0016:ldloc.1
IL_0017:ldloc.2
IL_0018:callvirt实例bool[mscorlib]System.Collections.IEnumerator:：MoveNext（）
IL_001d:brtrue.s IL_000f
问题就在这里
IL_001f：离开IL_0035
}//结束，再试一次
最后
{
IL_0024:ldloc.2
IL_0025:isinst[mscorlib]System.IDisposable
IL_002a:stloc.3
IL_002b:ldloc.3
IL_002c:brfalse.s IL_0034
IL_002e:ldloc.3
IL_002f:callvirt实例void[mscorlib]System.IDisposable:：Dispose（）
IL_0034：最终结束
}//结束处理程序
IL_0035:ret
}//方法ForeachType:：Map的结尾

请您澄清一下为什么会出现“离开”指令？

谢谢您的建议。下面解释发生了什么

public virtual void BeginFinallyBlock() 
{
    if (m_currExcStackCount==0) { 
        throw new NotSupportedException(Environment.GetResourceString("Argument_NotInExceptionBlock"));
    }
    __ExceptionInfo current = m_currExcStack[m_currExcStackCount-1];
    int         state = current.GetCurrentState(); 
    Label       endLabel = current.GetEndLabel();
    int         catchEndAddr = 0; 
    if (state != __ExceptionInfo.State_Try) 
    {
        // generate leave for any preceeding catch clause 
        this.Emit(OpCodes.Leave, endLabel);
        catchEndAddr = m_length;
    }

    MarkLabel(endLabel);


    Label finallyEndLabel = this.DefineLabel();
    current.SetFinallyEndLabel(finallyEndLabel); 

    // generate leave for try clause
    this.Emit(OpCodes.Leave, finallyEndLabel); HERE'S THE ANSWER
    if (catchEndAddr == 0) 
        catchEndAddr = m_length;
    current.MarkFinallyAddr(m_length, catchEndAddr); 
}

---

我相信这是终止任何

try{}

块的IL要求。也许，但同样的手写代码有

leave.s

指令。如果我插入

leave.s

有两条说明我不确定我是否完全理解你在这里说的话，但是

leave

和

leave.s

是相同的说明，除了目标标签的允许范围。是的，相同，我没有插入

leave

说明。真奇怪。为什么相同的代码有不同的指令？手写的有leave.s和我的代码leave。只要看一看，它就很明显是从哪里来的。嗯，你能解释一下吗，对我来说，代码是正确的，但注释不是：）实际上是这个方法中的低代码块被注释了

//generate leave for try子句

，它添加了您正在寻找的假期-正如Ben指出的，代码中缺少

catch

子句意味着这个块，已注释的

//为任何前面的catch子句生成休假

是不相关的。

.method public virtual instance void  Map(class [mscorlib]System.Collections.IEnumerable A_1) cil managed
{
  // Code size       54 (0x36)
  .maxstack  5
  .locals init (class [mscorlib]System.Collections.Generic.List`1<int32> V_0,
           object V_1,
           class [mscorlib]System.Collections.IEnumerator V_2,
           class [mscorlib]System.IDisposable V_3)
  IL_0000:  newobj     instance void class [mscorlib]System.Collections.Generic.List`1<int32>::.ctor()
  IL_0005:  stloc.0
  IL_0006:  ldarg.1
  IL_0007:  callvirt   instance class [mscorlib]System.Collections.IEnumerator [mscorlib]System.Collections.IEnumerable::GetEnumerator()
  IL_000c:  stloc.2
  .try
  {
    IL_000d:  br.s       IL_0017
    IL_000f:  ldloc.2
    IL_0010:  callvirt   instance object [mscorlib]System.Collections.IEnumerator::get_Current()
    IL_0015:  stloc.1
    IL_0016:  ldloc.1
    IL_0017:  ldloc.2
    IL_0018:  callvirt   instance bool [mscorlib]System.Collections.IEnumerator::MoveNext()
    IL_001d:  brtrue.s   IL_000f

    THE ISSUE IS HERE
    IL_001f:  leave      IL_0035
  }  // end .try
  finally
  {
    IL_0024:  ldloc.2
    IL_0025:  isinst     [mscorlib]System.IDisposable
    IL_002a:  stloc.3
    IL_002b:  ldloc.3
    IL_002c:  brfalse.s  IL_0034
    IL_002e:  ldloc.3
    IL_002f:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_0034:  endfinally
  }  // end handler
  IL_0035:  ret
} // end of method ForeachType::Map

public virtual void BeginFinallyBlock() 
{
    if (m_currExcStackCount==0) { 
        throw new NotSupportedException(Environment.GetResourceString("Argument_NotInExceptionBlock"));
    }
    __ExceptionInfo current = m_currExcStack[m_currExcStackCount-1];
    int         state = current.GetCurrentState(); 
    Label       endLabel = current.GetEndLabel();
    int         catchEndAddr = 0; 
    if (state != __ExceptionInfo.State_Try) 
    {
        // generate leave for any preceeding catch clause 
        this.Emit(OpCodes.Leave, endLabel);
        catchEndAddr = m_length;
    }

    MarkLabel(endLabel);


    Label finallyEndLabel = this.DefineLabel();
    current.SetFinallyEndLabel(finallyEndLabel); 

    // generate leave for try clause
    this.Emit(OpCodes.Leave, finallyEndLabel); HERE'S THE ANSWER
    if (catchEndAddr == 0) 
        catchEndAddr = m_length;
    current.MarkFinallyAddr(m_length, catchEndAddr); 
}