Override Default Constructor of Partial Class with Another Partial Class

Question

I don\'t think this is possible, but if is then I need it :)

I have a auto-generated proxy file from the wsdl.exe command line tool by Visual Studio 2008.

Th

Answer 1

I'm not quite addressing the OP, but if you happen to be generating classes with the EntityFramework Reverse POCO Generator, there's a partial method called in the constructor which is handy for initializing things you're adding via partial classes on your own...

Generated by tool:

   [System.CodeDom.Compiler.GeneratedCode("EF.Reverse.POCO.Generator", "2.37.3.0")]
    public partial class Library {
        public string City { get; set; }
        public Library() {
            InitializePartial();
        }
        partial void InitializePartial();
    }

added by you:

    public partial class Library {
        List<Book> Books { get; set; }
        partial void InitializePartial() {
            Books = new List<Book>();
        }
    }

    public class Book {
        public string Title { get; set; }
    }

Answer 2

For a Web service proxy generated by Visual Studio, you cannot add your own constructor in the partial class (well you can, but it does not get called). Instead, you can use the [OnDeserialized] attribute (or [OnDeserializing]) to hook in your own code at the point where the web proxy class is instantiated.

using System.Runtime.Serialization;

partial class MyWebService
{
     [OnDeserialized]
     public void OnDeserialized(StreamingContext context)
     {
         // your code here
     }
}

Answer 3

This is not possible. Partial classes are essentially parts of the same class; no method can be defined twice or overridden, and that includes the constructor.

You could call a method in the constructor, and only implement it in the other part file.

Answer 4

Sometimes you don't have access or it's not allowed to change the default constructor, for this reason you cannot have the default constructor to call any methods.

In this case you can create another constructor with a dummy parameter, and make this new constructor to call the default constructor using ": this()"

public SomeClass(int x) : this()
{
    //Your extra initialization here
}

And when you create a new instance of this class you just pass dummy parameter like this:

SomeClass objSomeClass = new SomeClass(0);

Answer 5

I am thinking you might be able to do this with PostSharp, and it looks like someone has done just what you want for methods in generated partial classes. I don't know if this will readily translate to the ability to write a method and have its body replace the constructor as I haven't given it a shot yet but it seems worth a shot.

Edit: this is along the same lines and also looks interesting.

Answer 6

Hmmm, I think one elegant solution would be the following:

//* AutogenCls.cs file
//* Let say the file is auto-generated ==> it will be overridden each time when
//* auto-generation will be triggered.
//*
//* Auto-generated class, let say via xsd.exe
//*
partial class AutogenCls
{
    public AutogenCls(...)
    {
    }
}



//* AutogenCls_Cunstomization.cs file
//* The file keeps customization code completely separated from 
//* auto-generated AutogenCls.cs file.
//*
partial class AutogenCls
{
    //* The following line ensures execution at the construction time
    MyCustomization m_MyCustomizationInstance = new MyCustomization ();

    //* The following inner&private implementation class implements customization.
    class MyCustomization
    {
        MyCustomization ()
        {
            //* IMPLEMENT HERE WHATEVER YOU WANT TO EXECUTE DURING CONSTRUCTION TIME
        }
    }
}

This approach has some drawbacks (as everything):

1. It is not clear when exactly will be executed the constructor of the MyCustomization inner class during whole construction procedure of the AutogenCls class.

2. If there will be necessary to implement IDiposable interface for the MyCustomization class to correctly handle disposing of unmanaged resources of the MyCustomization class, I don't know (yet) how to trigger the MyCustomization.Dispose() method without touching the AutogenCls.cs file ... (but as I told 'yet' :)

But this approach offers great separation from auto-generated code - whole customization is separated in different src code file.

enjoy :)