System.NotImplementedException

An interface can only have public methods. You might consider using an abstract base class with a protected abstract method AddError for this. The base class can then implement the IValidationCRUD interface, but only after you have removed the private method.

like this:

public interface IValidationCRUD
{
    ICRUDValidation IsValid(object obj);
}

public abstract class ValidationCRUDBase: IValidationCRUD {
    public abstract ICRUDValidation IsValid(object obj);
    protected abstract void AddError(ICRUDError error);
}

By Botz3000. Read the original answer on Stack Overflow.

I'm surprised AutoMapper hasn't come up as an answer.

As is clear from all the previous answers, you cannot do the typecast. However, using AutoMapper, in a few lines of code you can have a new SkyfilterClient instantiated based on an existing NetworkClient.

In essence, you would put the following where you are currently doing your typecasting:

using AutoMapper;
...
// somewhere, your network client was declared
var existingNetworkClient = new NetworkClient();
...
// now we want to type-cast, but we can't, so we instantiate using AutoMapper
AutoMapper.Mapper.CreateMap<NetworkClient, SkyfilterClient>();
var skyfilterObject = AutoMapper.Mapper.Map<SkyfilterClient>(existingNetworkClient);

Here's a full-blown example:

  public class Vehicle
  {
    public int NumWheels { get; set; }
    public bool HasMotor { get; set; }
  }

  public class Car: Vehicle
  {
    public string Color { get; set; }
    public string SteeringColumnStyle { get; set; }
  }

  public class CarMaker
  {
    // I am given vehicles that I want to turn into cars...
    public List<Car> Convert(List<Vehicle> vehicles)
    {
      var cars = new List<Car>();
      AutoMapper.Mapper.CreateMap<Vehicle, Car>(); // Declare that we want some automagic to happen
      foreach (var vehicle in vehicles)
      {
        var car = AutoMapper.Mapper.Map<Car>(vehicle);
        // At this point, the car-specific properties (Color and SteeringColumnStyle) are null, because there are no properties in the Vehicle object to map from.
        // However, car's NumWheels and HasMotor properties which exist due to inheritance, are populated by AutoMapper.
        cars.Add(car);
      }
      return cars;
    }
  }

By HeyZiko. Read the original answer on Stack Overflow.

This happens because of NSubstitute syntax specific. For example in:

((IQueryable<Blog>) mockSet).Provider.Returns(data.Provider);

NSubstitute calls the Provider's getter, then it specifies the return value. This getter call isn't intercepted by the substitute and you get an exception. It happens because of explicit implementation of IQueryable.Provider property in DbQuery class.

You can explicitly create substitutes for multiple interfaces with NSub, and it creates a proxy which covers all specified interfaces. Then calls to the interfaces will be intercepted by the substitute. Please use the following syntax:

// Create a substitute for DbSet and IQueryable types:
var mockSet = Substitute.For<DbSet<Blog>, IQueryable<Blog>>();
    
// And then as you do:
((IQueryable<Blog>) mockSet).Provider.Returns(data.Provider);
((IQueryable<Blog>) mockSet).Expression.Returns(data.Expression);
((IQueryable<Blog>) mockSet).ElementType.Returns(data.ElementType);
((IQueryable<Blog>) mockSet).GetEnumerator().Returns(data.GetEnumerator());

By Alexandr Nikitin. Read the original answer on Stack Overflow.

Per the C#9 record proposal, the following should compile, even if not very useful without actual implementations..

// No explicit IEquatable<R> - this is synthesized!
public sealed record SimpleVo
{
    // Not virtual, as SimpleVo (R) is sealed.
    // Accepts SimpleVo? (R?), and not SimpleVo (R), as argument.
    public bool Equals(SimpleVo? other) =>
        throw new System.NotImplementedException();

    // Optional: warning generated if not supplied when Equals(R?) is user-defined. 
    // Must have the override modifier, because System.Object already defines int GetHashCode().
    public override int GetHashCode() =>
        throw new System.NotImplementedException();

    // No other “standard” equality members!
}

There are restrictions on the equality-related members as most of the code is synthesized. The proposal includes examples of the expected synthesized underlying type.

That is, given just a Equals(R?) the compiler creates a ==, !=, and Equals(object). The methods that can be defined can be found by searching for “user-defined” in the proposal.

Attempting to override/define other equality methods or operators is expected to fail:

It is an error if the override is declared explicitly.

The behavior is discussed in ‘Equality members’ and is summarized in the paragraph:

The record type implements System.IEquatable<R> and includes a synthesized strongly-typed overload of bool Equals(R? other) where R is the record type. The method is public, and the method is virtual unless the record type is sealed. The [Equals(R?)] method can be declared explicitly. It is an error if the explicit declaration does not match the expected signature or accessibility, or the explicit declaration doesn't allow overriding it in a derived type and the record type is not sealed. If Equals(R? other) is user-defined (not synthesized) but GetHashCode is not [user-defined], a warning is produced.

By user2864740. Read the original answer on Stack Overflow.