C#’s equivalent to VB.NET’s DirectCast

It seems clear that the functionality you want is not in C#. Try this though…

static T DirectCast<T>(object o, Type type) where T : class
{
    if (!(type.IsInstanceOfType(o)))
    {
        throw new ArgumentException();
    }
    T value = o as T;
    if (value == null && o != null)
    {
        throw new InvalidCastException();
    }
    return value;
}

Or, even though it is different from the VB, call it like:

static T DirectCast<T>(object o) where T : class
{
    T value = o as T;
    if (value == null && o != null)
    {
        throw new InvalidCastException();
    }
    return value;
}