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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

Quote:

A large list of construction parameters, like any large parameter list, is a CodeSmell. Usually when I see these I find that many of the parameters are DataClumps and should be replaced by their own object. Having said that it's not unusual for constructor methods to have more parameters than other methods - but they are a good place to spot data clumps.