Interface Contravariance

InterfaceContravariance.cs

 public interface IContravariantExample<in T>
{
    string Go(T t);
}
public class ContravariantExample<T> : IContravariantExample<T>
{
    public string Go(T t) => $"{nameof(ContravariantExample<T>)} {typeof(T).Name} {t.GetType().Name} {t}"; 
}

[Fact]
public void InterfaceContraVariance()
{
    object o = "13";
    IContravariantExample<object> ino = new ContravariantExample<object>();
    IContravariantExample<string> ins = ino;
    const string expected = "ContravariantExample Object String 13";

    string s1 = ino.Go(o);
    Assert.Equal(expected, s1);

    string s2 = ins.Go(o as string);
    Assert.Equal(expected, s2);
}