generic NOT constraint where T : !IEnumerable

Question

As per the title, is it possible to declare type-negating constraints in c# 4 ?

Answer 1

As far as I know a Not contraint is not possible. You CAN use base classes and/or Interfaces to constrain a Generic. Faced with a similar problem leading to runtime failures, I implemented an interface on the classes the Generic was to handle:

public interface IOperations
{

}

public static T GenericOperationsFactory(ILogger loggerInstance, ref ExecutionContext executionContext) 
        where T: IOperations
{
    var operationsContext = Factories.OperationsContextFactory(loggerInstance, ref executionContext);

    var operations = typeof(T).GetConstructor(new[] { typeof(OperationsContext) }).Invoke(new object[] { operationsContext });

    return (T)operations;
}

public abstract class OperationsBase:IOperations
{
    protected OperationsContext Context { get; set; }

    public OperationsBase(OperationsContext context)
    {
        Context = context;
    }
...

public class ListsOperations : OperationsBase
{
    public ListsOperations(OperationsContext context) :
        base(context)
    {

    }

alternatively:

public static T GenericOperationsFactory(ILogger loggerInstance, ref ExecutionContext executionContext) 
        where T: OperationsBase
{
    var operationsContext = Factories.OperationsContextFactory(loggerInstance, ref executionContext);

    var operations = typeof(T).GetConstructor(new[] { typeof(OperationsContext) }).Invoke(new object[] { operationsContext });

    return (T)operations;
}

public abstract class OperationsBase
{
    protected OperationsContext Context { get; set; }

    public OperationsBase(OperationsContext context)
    {
        Context = context;
    }
...

public class ListsOperations : OperationsBase
{
    public ListsOperations(OperationsContext context) :
        base(context)
    {

    }