RemoveAt() not working c#

Question

Even after the RemoveAt() method, my list keeps being the same and I don't even get an error:

foreach (var row in queryCandidates.ToList())
{
    try
    {
        xString = queryCandidates.ToList().ElementAt(i).District;
        int.TryParse(xString, out xNumber);

        temp = xNumber.Equals(districtNumber);
        System.Diagnostics.Debug.Write(temp+ " ");
        System.Diagnostics.Debug.Write(i+" ");
        if (temp == false)
        {
            System.Diagnostics.Debug.WriteLine(" i is:"+i);

            //not working even when it should
            queryCandidates.ToList().RemoveAt(i);

        }
    }

    catch { }
    i++;
    if (last == i)
    {
        System.Diagnostics.Debug.WriteLine("before ending loop: ");
        return View(queryCandidates.ToList());
    }
}

System.Diagnostics.Debug.WriteLine("after ending the loop: ");
return View(queryCandidates.ToList());

Answer 1

ToList() creates a new instance. From this instance you are removing the element. You are not removing the element from the original enumerable.

You should be doing something like this instead:

var candidates = queryCandidates.ToList();
var elementsToRemove = new List<int>();
foreach (var row in candidates)
{
    // ...
    xString = candidates[i].District;
    // ...
    if (temp == false)
    {             
        // ... 
        elementsToRemove.Add(i);
    }  
}

for(int i = elementsToRemove.Count - 1; i >= 0; --i)
    candidates.RemoveAt(elementsToRemove[i]);

return View(candidates);

Please note the use of elementsToRemove. You can't remove the items directly in the loop. This will throw an exception.

---

Additionally, please note that ToList copies all data. Every single time you call it. It should be obvious that this is not a good idea to do in a loop.