Build List from unshared items from two other Lists

Question

Ultimately, my goal is to take two lists and then generate a third consisting of items that the first two lists do NOT share. I am able to get the results I want using two foreach loops, but I am hoping to learn about some magical List tool that will do it more cleanly.

public List<string> removeMatchingItems(List<string> List1, List<string> List2)
{
    List<string> desiredList = new List<string>();

    foreach (string value in List1)
    {
        if (!List2.Contains(value))
        { desiredList.Add(value); }
    }
    foreach (string value in List2)
    {
        if (!List1.Contains(value))
        { desiredList.Add(value); }
    }
    return desiredList;
}

Answer 1

The operation is called the symmetric difference of List1 and List2. You can write

return list1.Except(list2).Union(list2.Except(list1)).ToList<string>();

Answer 2

First of all I am going to complain about your if blocks and the way that you brace them. I don't like it and I don't think many other people would enjoy it either.

if (condition)
{
    //Do Work
}

This might be more of a personal preference, but I would rather call this method GetMisMatchedItems. Something that I did here without even realizing it is that I used PascalCasing for the Method name instead of camelCasing, this is a C# standard.

With these changes I think it looks much cleaner looking.

public List<string> GetMisMatchedItems(List<string> List1, List<string> List2)
{
    List<string> desiredList = new List<string>();

    foreach (string value in List1)
    {
        if (!List2.Contains(value))
        { 
            desiredList.Add(value); 
        }
    }
    foreach (string value in List2)
    {
        if (!List1.Contains(value))
        { 
            desiredList.Add(value); 
        }
    }
    return desiredList;
}