Does foreach evaluate the array at every iteration?

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I just mocked your code with this

foreach(var v in Enumerable.Range(1,10).Skip(1))
    v.Dump();

And here is the IL generated.

IL_0001:  nop         
IL_0002:  ldc.i4.1    
IL_0003:  ldc.i4.s    0A 
IL_0005:  call        System.Linq.Enumerable.Range
IL_000A:  ldc.i4.1    
IL_000B:  call        System.Linq.Enumerable.Skip//Call to Skip
IL_0010:  callvirt    System.Collections.Generic.IEnumerable<System.Int32>.GetEnumerator
IL_0015:  stloc.1     // CS$5$0000
IL_0016:  br.s        IL_0026
IL_0018:  ldloc.1     // CS$5$0000
IL_0019:  callvirt    System.Collections.Generic.IEnumerator<System.Int32>.get_Current
IL_001E:  stloc.0     // v
IL_001F:  ldloc.0     // v
IL_0020:  call        LINQPad.Extensions.Dump
IL_0025:  pop         
IL_0026:  ldloc.1     // CS$5$0000
IL_0027:  callvirt    System.Collections.IEnumerator.MoveNext
IL_002C:  stloc.2     // CS$4$0001
IL_002D:  ldloc.2     // CS$4$0001
IL_002E:  brtrue.s    IL_0018
IL_0030:  leave.s     IL_0042
IL_0032:  ldloc.1     // CS$5$0000
IL_0033:  ldnull      
IL_0034:  ceq         
IL_0036:  stloc.2     // CS$4$0001
IL_0037:  ldloc.2     // CS$4$0001
IL_0038:  brtrue.s    IL_0041
IL_003A:  ldloc.1     // CS$5$0000
IL_003B:  callvirt    System.IDisposable.Dispose
IL_0040:  nop         
IL_0041:  endfinally

As you can see Skip is called only once.

Equivalent c# code would look something like this

IEnumerator<int> e = ((IEnumerable<int>)values).GetEnumerator();//Get the enumerator
try
{
  int m;//This variable is here prior to c#5.0
  while(e.MoveNext())
  {//int m; is declared here starting from c#5.0
    m = (int)(int)e.Current;
    //Your code here
  }
}
finally
{
  if (e != null) ((IDisposable)e).Dispose();
}

Consider the below code, If foreach calls VeryLongRunningMethodThatReturnsEnumerable at each iteration then that would be nightmare. Huge flaw in the design of the language. Fortunately it doesn’t do that.

foreach(var obj in VeryLongRunningMethodThatReturnsEnumerable())
{
   //Do something with that obj
}

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