Override Default Constructor of Partial Class with

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.

The proxy output is partial classes. I want to override the default constructor that is generated. I would rather not modify the code since it is auto-generated.

I tried making another partial class and redefining the default constructor, but that doesn't work. I then tried using the override and new keywords, but that doesn't work.

I know I could inherit from the partial class, but that would mean I'd have to change all of our source code to point to the new parent class. I would rather not have to do this.

Any ideas, work arounds, or hacks?

//Auto-generated class
namespace MyNamespace {
   public partial class MyWebService : System.Web.Services.Protocols.SoapHttpClientProtocol {
      public MyWebService() {
         string myString = "auto-generated constructor";
         //other code...
      }
   }
}

//Manually created class in order to override the default constructor
namespace MyNamespace {
   public partial class MyWebService : System.Web.Services.Protocols.SoapHttpClientProtocol {
      public override MyWebService() { //this doesn't work
         string myString = "overridden constructor";
         //other code...
      }
   }
}

Answer 1

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 2

Actually, this is now possible, now that partial methods have been added. Here's the doc:

http://msdn.microsoft.com/en-us/library/wa80x488.aspx

Basically, the idea is that you can declare and call a method in one file where you are defining the partial class, but not actually define the method in that file. In the other file, you can then define the method. If you are building an assembly where the method is not defined, then the ORM will remove all calls to the function.

So in the case above it would look like this:

//Auto-generated class

namespace MyNamespace {
   public partial class MyWebService : System.Web.Services.Protocols.SoapHttpClientProtocol {
      public MyWebService() {
         string myString = "auto-generated constructor";
         OtherCode();
      }
   }
}

partial void OtherCode();

//Manually created class in order to override the default constructor

partial void OtherCode()
{
   //do whatever extra stuff you wanted.
}

It is somewhat limited, and in this particular case, where you have a generated file that you'd need to alter, it might not be the right solution, but for others who stumbled on this trying to override functionality in partial classes, this can be quite helpful.

Answer 3

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 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

You can't do this. I suggest using a partial method which you can then create a definition for. Something like:

public partial class MyClass{ 

    public MyClass(){  
        ... normal construction goes here ...
        AfterCreated(); 
    }

    public partial void OnCreated();
}

The rest should be pretty self explanatory.

EDIT:

I would also like to point out that you should be defining an interface for this service, which you can then program to, so you don't have to have references to the actual implementation. If you did this then you'd have a few other options.