示例

// cs1957.cs
class Base<T, S>
{
    public virtual string Test(out T x) // CS1957
    {
        x = default(T);
        return "Base.Test";
    }
    public virtual void Test(ref S x) { }
}

class Derived : Base<int, int>
{
    public override string Test(out int x)
    {
        x = 0;
        return "Derived.Test";
    }

    static int Main()
    {
        int x;
        if (new Derived().Test(out x) == "Derived.Test")
            return 0;
        return 1;
    }
}