How to replace java wildcard in c#?

Question

Java

Rewriting code from java to .net c# ran into a problem with transferring classes from wildcard. There are two classes

public abstract class Client<T extends Connection<?>>
public class Connection<T extends Client<?>>

I thought it could be done like this

public abstract class Client<T> where Connection<U>

but it turns out that it doesn't even work.

public abstract class Client<T, U> where Connection<T, U>
public abstract class Connection<T, U> where Client<T, U>

so how do you get out of the situation? And do I need to bathe;) thank you all