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Explanation

I use the xsd.exe tool to generate a class API based upon an XSD (defines a schema for XML files) from which to interact with XML files.

This tool works well, but this issue is that I have a few schemas which are by-and-large identical with small tweaks, so I want to create interfaces or abstract classes that allow me to reuse code elsewhere.

In my example below I've simplified the generated code for purposes of sharing it here but the principle still holds.

Example Non-Functioning Code

Program.cs

public static void Main()

 BaseColor baseColor = new Color1 ColorDescription = "Red" ;
 BaseShape baseShape = new Shape1 Content = baseColor ;

Models.cs

//Auto generated models - I have no control over these but they are partial classes

//First set of autogenerated models, normally in its own file
public partial class Shape1

 public Color1 Content get; set; 


public partial class Color1


 public string ColorDescription get; set; 


//Second set of autogenerated models, normally in its own file
public partial class Shape2

 public Color2 Content get; set; 


public partial class Color2


 public string ColorDescription get; set; 


//Attemping to abstract these classes so I can generically use them regardless of underlying type
public abstract class BaseShape

 public abstract BaseColor Content get; set; 


public abstract class BaseColor

 public abstract string ColorDescription get; set; 


//Attempting to extend the autogenerated classes with the abstract classes
public partial class Shape1 : BaseShape 

public partial class Color1 : BaseColor 

public partial class Shape2 : BaseShape 

public partial class Color2 : BaseColor 

Errors

This error is repeated 8 times in total for both shapes, both colors and both get/set methods.

'Shape1' does not implement inherited abstract member 'BaseShape.Content.set' XmlSerializeChild

And from the Main method.

Cannot implicitly convert type 'XmlSerializeChild.Models.BaseColor' to 'XmlSerializeChild.Models.Color1'. An explicit conversion exists (are you missing a cast?)

You where quite close, but as TheGeneral wrote in his comment, you can't change the type of the property when overriding it.

What you can do is introduce a new property (I've chosen to use interfaces but it will work just as well with abstract classes) that will be used in the code, having the explicit cast in each partial class:

So first, I've created the interfaces:

public interface IColor string ColorDescription get; set; 

public interface IShape IColor BaseContent get; set; 

Then, added the IColor implementation to the Color1 and Color2 classes:

public partial class Color1 : IColor 
public partial class Color2 : IColor 

(That was the easy part since the ColorDescription is the same type for both colors).

Next, I've added the IShape implementation to the Shape1 and Shape2 classes:

public partial class Shape1 : IShape 

 public IColor BaseContent
 
 get return Content; 
 set Content = (Color1) value; 
 


public partial class Shape2 : IShape 

 public IColor BaseContent
 
 get return Content; 
 set Content = (Color2) value; 
 

Now, in the Main method, you can do this:

var baseColor = new Color1() ColorDescription = "Red" ;
var baseShape = new Shape1() BaseContent = baseColor ;

Another option instead of introducing a new property would be to implicitly implement the IShape interface - but this would be more cumbersome and will not allow you to use the new Shape1() Content = baseColor syntax. Still, let's review this option as well:

So we rename the BaseContent property in the IShape interface:

interface IShape IColor Content get; set; 

And we implement it like this:

public partial class Shape1 : IShape 

 IColor IShape.Content 
 
 get return ((Shape1)this).Content; 
 set ((Shape1)this).Content = (Color1) value; 
 


public partial class Shape2 : IShape 

 IColor IShape.Content 
 
 get return ((Shape2)this).Content; 
 set ((Shape2)this).Content = (Color2) value; 
 

Then, we create our reverences like this:

var baseColor = new Color1() ColorDescription = "Red" ;
// Note: Do not use var here - you need the reference to be of type `IShape`!
IShape baseShape = new Shape1();
baseShape.Content = baseColor;