C# compiler complains that abstract class does not implement interface?

Question

I have a nice interface, and I want to implement one member of it in a base class so the clients can derive from the base class and have less boiler-plate to write. However, even though declared abstract, the compiler complains that the class does not implement the interface?!? How is this supposed to be done?

Code in question:

public interface ITaskDefinition {     ITask CreateTask(TaskId id);     string Name { get; }     bool HasName { get; } }  public abstract class TaskDefinitionBase : ITaskDefinition {     private string name_ = null;      public void SetName(string name)     {         name_ = name;     }      public string Name     {         get         {             return name_;         }     }      public bool HasName     {         get         {             return name_ != null;         }     } } 

and the error I get is:

ITaskDefinition.cs(15,27): error CS0535: 'NetWork.Task.TaskDefinitionBase' does not implement interface member 'NetWork.Task.ITaskDefinition.CreateTask(NetWork.Task.TaskId)' 

Answer 1

You must add an abstract stub of the method:

public abstract ITask CreateTask(TaskId id); 

Inheritors can then override it to implement the interface.