String.Format isn't working

Question

public override string ToString()
{
    string token = "something";
    foreach (something item in this)
    {
        something = something + "Some_Point({0},{1}),";
        string.Format(something, item.X, item.Y);
    }
    return something+= "anything";
}

This is the overridden ToString() method of a custom collection. The problem here is that String.Format isn't substituting the values of X and Y. It does substitute whenever I add return before String.Format. I am just starting to learn C# and have no idea what is causing this strange behaviour.

Answer 1

string.Format returns formatted string, you have to assign it back to your variable:

something = string.Format("Some_Point({0},{1}),", item.X, item.Y);