How to cast a list

I have a class A and a class B, class B is inherit from cla开发者_StackOverflow中文版ss A. Assume that I have:

A a1 = new B();
A a2 = new B();
List<A> LA = new List<A>{a1, a2};

Please help me how to convert List to List. I try to use List<B> LB = (List<B>)LA but get compiling error "Can't convert List<A> to List<B>".

Please help me. Thanks.

Note: only .NET 2.0. Thanks.

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You have to cast each item in the list, not the whole list.

List<A> listA = new List<A>();
List<B> listB = new List<B>();
for (int i = 0; i < listA.Count; i++)
{
    listB.Add((B)listA[i]);
}

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If you are in .NET 2.0, then I beleive that you are stuck enumerating over the list and casting each element independently. With .NET 3.5, you could use a "Select" extension method to cast them all with a single line of code.

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You can do it this way:

        List<A> la = new List<A>();
        List<B> lb = new List<B>();
        foreach( A a in la )
        {
            if (a is B)
                lb.Add((B)a);
            else
            {
                // ignore or throw an exeption
            }
        }

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Can you try something on these lines

LA.ForEach(delegate(A emp) { emp = (B)emp;  });