I've written a Web Service that has main service class. Let's call the
main class that exposes the service interface as Service1.

So, we have:

public class Service1: System.Web.Services.WebService
{
   //code
}

I also have a business object that I am going to name BusinessObject,
for example's sake. This object is built in the service module/dll as a
class like so:

namespace BusinessObjects
{
   public class BusinessObject
   {

       private SomeOtherClass mReferenceTypeMember;
       //the field mReferenceTypeMember is exposed through a property
called ReferenceTypeMember

       //code
       public BusinessObject()
       {
               //nothing for now
        }
   }
}

Note that there is only one default ctor for the BusinessObject class
and that doesn't do anything.

I compile. Build a DLL. Then I add a test project to this project. I
add a Web Reference in the Test project to point to the asmx for the
above-mentioned service. The test project and the service are both a
part of the same solution. The test project is created to test the
service.

In the test project I do,

//call the default constructor
TheAliasOfTheWebReference.Service1.BusinessObject bo = new
TheAliasOfTheWebReference.Service1.BusinessObject();

bo.ReferenceTypeMember.SomeValueTypeMember = "Value";

I get an object not set to an instance exception. Reasonable!

So, I go back to the service asmx.cs file and go straight to the class
BusinessObject and modify the default constructor to do this:

namespace BusinessObjects
{
   public class BusinessObject
   {

       private SomeOtherClass mReferenceTypeMember;
       //the field mReferenceTypeMember is exposed through a property
called ReferenceTypeMember

       //code
       public BusinessObject()
       {
               this.mRefrenceTypeMember = new SomeOtherClass();
        }
   }
}

Then, I rebuild the service.

I go to the test project. I delete the old Web Reference. I add a new
Web Reference to the same DLL  (I've burnt my fingers there in not
doing that).

I insert a breakpoint at the following line

//call the default constructor
TheAliasOfTheWebReference.Service1.BusinessObject bo = new
TheAliasOfTheWebReference.Service1.BusinessObject();

in the test project.

I expect it to step through the source code in my service. It doesn't.
And it still throws the object instance set to nothing exception.

What gives?