Multiple where for generic type

The latter syntax should be fine (and compiles for me). The first doesn't work because you're trying to provide two constraints on the same type parameter, not on different type parameters.

Please give a short but complete example of the latter syntax not working for you. This works for me:

public interface IFoo {}

public abstract class MyClass<T>
    where T : class, IFoo
{
}

A question about how to define multiple where clauses links here as a duplicate. If that question truly is a duplicate than this "complete" answer must contain both cases.

Case 1 -- Single generic has multiple constraints:

public interface IFoo {}

public abstract class MyClass<T>
    where T : class, IFoo
{
}

Case 2 -- Multiple generics each with their own constraints:

public interface IFoo1 {}
public interface IFoo2 {}

public abstract class MyClass<T1, T2>
    where T1 : class, IFoo1
    where T2 : IFoo2
{
}