c# - Strange behavior of Enumerator.MoveNext() -

could explain why code running in infinity loop? why movenext() return true always?

var x = new { templist = new list<int> { 1, 3, 6, 9 }.getenumerator() }; while (x.templist.movenext()) {   console.writeline("hello world"); } 

list<t>.getenumerator() returns mutable value type (list<t>.enumerator). you're storing value in anonymous type.

now, let's have @ does:

while (x.templist.movenext()) {     // ignore } 

that's equivalent to:

while (true) {     var tmp = x.templist;     var result = tmp.movenext();     if (!result)     {         break;     }      // original loop body } 

now note we're calling movenext() on - copy of value in anonymous type. can't change value in anonymous type - you've got property can call, give copy of value.

if change code to:

var x = new { templist = (ienumerable<int>) new list<int> { 1, 3, 6, 9 }.getenumerator() }; 

... you'll end getting reference in anonymous type. reference box containing mutable value. when call movenext() on reference, value inside box mutated, it'll want.

for analysis on similar situation (again using list<t>.getenumerator()) see my 2010 blog post "iterate, damn you!".