C# Create New T()

Solution 1:

Take a look at new Constraint

public class MyClass<T> where T : new()
{
    protected T GetObject()
    {
        return new T();
    }
}

T could be a class that does not have a default constructor: in this case new T() would be an invalid statement. The new() constraint says that T must have a default constructor, which makes new T() legal.

You can apply the same constraint to a generic method:

public static T GetObject<T>() where T : new()
{
    return new T();
}

If you need to pass parameters:

protected T GetObject(params object[] args)
{
    return (T)Activator.CreateInstance(typeof(T), args);
}

Solution 2:

Why hasn't anyone suggested Activator.CreateInstance ?

http://msdn.microsoft.com/en-us/library/wccyzw83.aspx

T obj = (T)Activator.CreateInstance(typeof(T));

Solution 3:

Another way is to use reflection:

protected T GetObject<T>(Type[] signature, object[] args)
{
    return (T)typeof(T).GetConstructor(signature).Invoke(args);
}

Solution 4:

The new constraint is fine, but if you need T being a value type too, use this:

protected T GetObject() {
    if (typeof(T).IsValueType || typeof(T) == typeof(string)) {
        return default(T);
    } else {
       return (T)Activator.CreateInstance(typeof(T));
    }
}