c# 中的 for vs foreach

var arr = Enumerable.Range(0, 100000000).ToList();
	
	var sw = Stopwatch.StartNew();
	for(var i = 0;i < arr.Count; i++){}
	sw.Stop();
	Console.WriteLine("for loop takes : " + sw.ElapsedTicks);
	
	sw = Stopwatch.StartNew();
	foreach(var x in arr){}
	sw.Stop();
	Console.WriteLine("for loop takes : " + sw.ElapsedTicks);

...
IL_0018:  ldc.i4.0    
IL_0019:  stloc.2     // i
IL_001A:  br.s        IL_0022
IL_001C:  nop         
IL_001D:  nop         
IL_001E:  ldloc.2     // i
IL_001F:  ldc.i4.1    
IL_0020:  add         
IL_0021:  stloc.2     // i
IL_0022:  ldloc.2     // i
IL_0023:  ldloc.0     // arr
IL_0024:  callvirt    System.Collections.Generic.List<System.Int32>.get_Count
IL_0029:  clt         
IL_002B:  stloc.s     04 // CS$4$0000
IL_002D:  ldloc.s     04 // CS$4$0000
IL_002F:  brtrue.s    IL_001C


...

...
IL_005A:  ldloc.0     // arr
IL_005B:  callvirt    System.Collections.Generic.List<System.Int32>.GetEnumerator
IL_0060:  stloc.s     05 // CS$5$0001
IL_0062:  br.s        IL_006E
IL_0064:  ldloca.s    05 // CS$5$0001
IL_0066:  call        System.Collections.Generic.List<System.Int32>+Enumerator.get_Current
IL_006B:  stloc.3     // x
IL_006C:  nop         
IL_006D:  nop         
IL_006E:  ldloca.s    05 // CS$5$0001
IL_0070:  call        System.Collections.Generic.List<System.Int32>+Enumerator.MoveNext
IL_0075:  stloc.s     04 // CS$4$0000
IL_0077:  ldloc.s     04 // CS$4$0000
IL_0079:  brtrue.s    IL_0064
IL_007B:  leave.s     IL_008C
IL_007D:  ldloca.s    05 // CS$5$0001
IL_007F:  constrained. System.Collections.Generic.List<>.Enumerator
IL_0085:  callvirt    System.IDisposable.Dispose
IL_008A:  nop         
IL_008B:  endfinally  
IL_008C:  nop   
...

for loop takes : 764538
for loop takes : 1311252

c# 中的 for vs foreach

原文：http://blog.csdn.net/lan_liang/article/details/50353241