Design without default constructor

Question

I want to restrict creating object using default constructor. Because I have a desing like below:

class Program
{
    static void Main(string[] args)
    {
        BaseClass bc = new BaseClass("","");
        XmlSerializer xml = new XmlSerializer(typeof(BaseClass));
        StreamWriter sw = new StreamWriter(File.Create("c:\\test.txt"));
        xml.Serialize(sw,bc);
        sw.Flush();
        sw.Close();
    }
}
[Serializable]
public class BaseClass
{
    public string UserName, Password;
    // I don't want to create default constructor because of Authentication
    public BaseClass(string _UserName, string _Password)
    {
        UserName = _UserName;
        Password = _Password;
        f_Authenticate();
    }
    private void f_Authenticate() { }
}

public class DerivedClass:BaseClass
{
    public DerivedClass(string _UserName, string _Password) : base(_UserName, _Password)
    {
    }
}

This is ok. But when I make BaseClass to Serializable it'll generate this error: Unhandled Exception: System.InvalidOperationException: ConsoleApplication1.BaseC lass cannot be serialized because it does not have a parameterless constructor.

Now my design is collapsing because I need to have Username, Password parameters but default constructor is ruining my design....

What should I do?

Answer 1

Create a private default constructor

private DerivedClass()
{
    // code
}

The serialzer will successfully call this even though it's private