Welcome to the Lounge

Super Lloyd wrote:

In his defence he has an argument. If someone use that DTO as well, the compiler will force them to initialise all values.

var dto = new FooDto(actualT1Val,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null);

Super Lloyd wrote:

select your favourite of 2 options.

public class FooDto
{
  public static FooDto From(MyFooClass c)
  {
    // ...mapping...
  }
}

public class FooDto : IFooDto
{
  public static IFooDto From(IFooClass c)
  {
    // ...mapping...
  }
}

public class FooDto
{
   public FooDto(MyFooClass foo)
   {
        Property1 = foo.property1;
        // .....
        Property24 = foo.property24;
   }

   public T1 Property1 { get; }
   // ....
   public T24 Property24 { get; }
}
// ....
class MyFooClass
{
    private T1 property1;
    // ....
    private T24 property24;
}

public class Foo
{
  public class DTO
  {
    public T1 P1 { set; get; } = P1_default_value;
...
    public T24 P24 { set; get; } = P24_default_value;
  }

  public void In(DTO dto)
  {
    // Set _P* from dto.P*
  }

  public DTO Out()
  {
    DTO dto = new DTO();

    // set dto.P* from _P*

    return dto;
  }

  private T1 _P1;
...
  private T24 _P24;
}

Foo foo = new Foo();
...
foo.In(new DTO() { P3 = Fred, P17 = Wilma; });
Foo foo2 = new Foo();
foo2.In(foo.Out());

public class FooDto
{
   public FooDto(T1 value1 /** 24 values later */, T24 value24)
   {
        Property1 = value1;
        // .....
        Property24 = value24;
   }

   public T1 Property1 { get; }
   // ....
   public T24 Property24 { get; }
}
// ....
class MyFooClass : FooDto
{
// ....
}

public class FooDto