Question

The following code:

    private IList<T> DoStuff<T>()
    {
        IList<T> res = new List<T>();
        for (int i = 0; i < 10; i++)
        {
            T item = DoOtherStuff<T>();
            res.Add(item);
        }
        return res;
    }

    private T DoOtherStuff<T>() where T : new()
    {
        return new T();
    }

Generates the following error:

‘T’ must be a non-abstract type with a public parameterless constructor in order to use it as parameter ‘T’ in the generic type or method ‘DoOtherStuff()’

Please may somebody explain why?

Answer 1

Change

private IList<T> DoStuff<T>()

to

private IList<T> DoStuff<T>() where T : new()

since otherwise you can’t guarantee that T has a new() constructor.