using QuickFix.StringField;
using QuickFix.DoubleField;

public class MyStringField:StringField
{
  public MyStringField() : base(6123) {}
  public MyStringField(String data) : base(6123, data) {}
}

public class MyPriceField:DoubleField
{
  public MyPriceField() : base(8756) {}
  public MyPriceField(double data) : base(8756, data) {}
}