My edmx file generate some partial classes. I want extend functionality adding one property, but edmx file is in another assembly. In this case they are like two unrelated classes.
How can I solve this?
You can inherit another type from the entity type edmx has generated and add your property to the inherited one.
you can Create a new class in your assembly that will extend/inherit the partial class and add properties and methods as you like
Related
I have reverse engineered a MySQL database in a C# desktop app. What I would like to do is extend one of the model classes, so that I can add methods to it to use locally in my application. I don't want to change any properties or anything just. Just get information and calculate things.
The problem is that when I inherit from one of the model classes I get an error about a new discriminator field being in the class but not the database.
Is there a way to do what I want to do?
Given that the model classes are partial, you can just declare your own partial classes to join them:
// Note - needs to be in the same namespace as the auto-generated declaration
public partial class Foo
{
// Add your own methods here, which can refer to the properties declared
// for the same type in the auto-generated code
}
The point of partial classes is that multiple files can contribute source to the same type.
You could try extension methods to accomplish this instead of inheriting and creating a new subtype.
You would "attach" the extension methods to the model class which you generated.
Consider we create a partial class in Project1 and we have a Project2 that has reference to Project1 .How is it possible to declare some other method of partial class in Project2 ?
thanks
The partial construct is only a compiler functionality, to allow a class to be spread out in several source files. The compiled class still lives in one and only one class library (dll file).
There are two ways to extend a class in another library:
Inheritance, unless the class is sealed. This requires that the calling code handles all object instantiation to instantiate the new derived class.
Extension methods, which makes the code look like there are new methods on that class, but that is just syntactic sugar. It won't change the class itself.
It is not possible to extend a partial class in another project. Partial is only compiler sugar. The compiler will create only one class in the resulting assembly.
You can use the Extension methods that allow you to create additional methods for existing class
Partial classes cannot exist out side assembly boundaries!
I would like to start by saying that im new to EF, and the following text is just based on my assumptions. So feel free to correct me on where im wrong:
I have an entity generated by EF called Foo. I suppose this is an EntityObject. So if i create an instance of Foo, it will be an EntityObject.
But if i create a new partial class called Foo in my Entity Modifications folder, i will have a POCO version of it. I would like to know how to use the POCO instead of the EntityObject.
Suppose you have the following:
public partial class Foo : EntityObject { }
and
public partial class Foo {}
This will result in one class Foo that inherits from EntityObject. The partial keyword does not mean that you have multiple classes Foo, it means that you have one class Foo that is divided over several code files and the compiler will merge them for you. Here you can find some more documentation.
If you don't want to inherit from EntityObject but have real POCO's you should have a look at the T4 templates for generating POCO entities.
I've declared a partial class with name "BusinessLayer" in BL namespace, but now I want to add another class with same name, and with keyword "partial" in that namespace. But Whenever I try to add class with with name "BusinessLayer", I'm getting an error, saying I can't declared multiple classes with same name in a namespace. Then how can I use partial classes in a single namespace?
I would fix your code if you'd write some, even just as an example.
Anyway, you should tag both as "partial".
Any declaration of this class, anywhere, should have the "partial" keyword in order to allow it to compile properly.
All declarations of the class must have the partial keyword, otherwise they will be interpreted as different classes and being in the same namespace will cause a compile time error.
My best guess is you're missing a partial keyword somewhere.
Edit: By the way, partial classes can only be declared in the same assembly, iirc. So all parts of the partial class need to be in the same assembly.
How can i create a partial class at runtime?
Example: I have a class
public partial class A
{
}
I want to create partial of my A class at runtime from an XML file.
because I don't compile my project when any change in code.
I know this is little meaning less but i need this.
XOML files work for me?
The point of partial classes is to be able to define parts of it in different source files. In the end, after compilation, what you have is a regular class, indistinguishable of any other. So there is not such a thing as "instantiating a partial class".
The partial keyword is used to separate a class across multiple code files. The compiler merges them together into a single class.
MSDN: Partial Class Definitions
You can't.
A partial class doesn't exist in the CLR. It's more of a Visual Vtudio trick than anything else.