C# initialize a generic class of interface type with implementing class type [duplicate]

Question

I want to know whether the below is achievable my any means.

If an interface object can be initialized with the implement class ie I1 objI1 = new C1() why can't a generic of the interface be initialized with the generic of the implementing class.

public interface I1
{

}

public class C1: I1
{

}

public class C2<T>
{
   
}

internal class Program
{
    static void Main(string[] args)
    {
        C2<I1> obj = new C2<C1>();  //Cannot implicitly convert type C2<C1> to C2<I1>         
    }
}