Question

I have the below interface and concrete class.

I am getting an error of:

‘DAL.Model.Audit.Categories’ cannot implement ‘DAL.Interfaces.IAudit.Categories’ because it does not have the matching return type of ‘System.Collections.Generic.IEnumerable’.

Could anyone please explain what I am doing wrong here?

public interface IAudit
{
    IEnumerable<ICategory> Categories { get; set; }
    IEnumerable<IAuditAnswer> Answers { get; set; }
}

public class Audit : IAudit
{
    public List<ICategory> Categories { get; set; }
    public List<IAuditAnswer> Answers { get; set; }
}

Answer 1

You must respect the contract when implementing an interface:

public class Audit : IAudit
{
    public IEnumerable<ICategory> Categories { get; set; }
    public IEnumerable<IAuditAnswer> Answers { get; set; }
}

In the interface the 2 properties are defined as IEnumerable<T>, so in your implementing class you should use the same type instead of List<T>.