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copied!<p>it’s been fixed in C# 5.0, and the example above in C# 5.0 works but fails in earlier versions of C#. </p> <p>But be careful, it does not concern a for loop</p> <pre><code> static void Main() { IEnumerable<char> query = "aaa bbb ccc"; string lettersToRemove = "ab"; Console.WriteLine("\nOK with foreach:"); foreach (var item in lettersToRemove) { query = query.Where(c => c != item); } foreach (char c in query) Console.Write(c); //OK: Console.WriteLine("\nOK with foreach and local temp variable:"); query = "aaa bbb ccc"; foreach (var item in lettersToRemove) { var tmp = item; query = query.Where(c => c != tmp); } foreach (char c in query) Console.Write(c); /* An IndexOutOfRangeException is thrown because: firstly compiler iterates the for loop treating i as an outsite declared variable when the query is finnaly invoked the same variable of i is captured (lettersToRemove[i] equals 3) which generates IndexOutOfRangeException The following program writes aaa ccc instead of writing ccc: Each iteration gets the same variable="C", i (last one frome abc). */ //Console.WriteLine("\nNOK with for loop and without temp variable:"); //query = "aaa bbb ccc"; //for (int i = 0; i < lettersToRemove.Length; i++) //{ // query = query.Where(c => c != lettersToRemove[i]); //} //foreach (char c in query) Console.Write(c); /* OK The solution is to assign the iteration variable to a local variable scoped inside the loop This causes the closure to capture a different variable on each iteration. */ Console.WriteLine("\nOK with for loop and with temp variable:"); query = "aaa bbb ccc"; for (int i = 0; i < lettersToRemove.Length; i++) { var tmp = lettersToRemove[i]; query = query.Where(c => c != tmp); } foreach (char c in query) Console.Write(c); } </code></pre>

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