Why partial class in asp.net

So that does affect the mapping between database table and DBML entity but you can easily get an extra field. It means you can write the code on your own without messing with the system generated code. More than one developer can simultaneously work the code for the same class. You can maintain your application better by compacting large classes. Suppose you have a class that has multiple interfaces so you can create multiple source files depending on interface implements.

It is easy to understand and maintain an interface implemented on which the source file has a partial class. Let's see the following code snippet.

You need to use partial keyword in each part of partial class. The name of each part of partial class should be the same but source file name for each part of partial class can be different.

All parts of a partial class should be in the same namespace. Each part of a partial class should be in the same assembly or DLL, in other words you can't create a partial class in source files of a different class library project.

Each part of a partial class has the same accessibility. If you inherit a class or interface on a partial class then it is inherited on all parts of a partial class. If a part of a partial class is sealed then the entire class will be sealed. If a part of partial class is abstract then the entire class will be an abstract class. Example I will develop an example that explains how to use a partial class in your project. So you create a data context, in other words a. Each table creates a partial class in the data context designer file and each table field becomes a property for the table.

So you can extend your models with another partial class without be bothered by the automatic generation. When is it appropriate to use C partial classes? Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Why do we need partial Class in. NET [duplicate] Ask Question. Asked 6 years, 4 months ago.

Active 6 years, 4 months ago. Viewed 2k times. Improve this question. In some cases, auto generated files are generated as partial so they have some extensibility.

This can be very convenient. For example: Entity framework classes are partial so you can create enum properties that wrap integer fields. This may be the reason JavaScript doesn't support it. Add a comment. Active Oldest Votes. Partial classes provide a way to split the code of a class across files. Improve this answer. Emond Erno Emond Erno There are 3 reasons to have partial classes: For necessary seperation when creating designers and it should avoid the mixing of user and designer code.

For example: Windows Forms classes For splitting large classes, however this should be avoided anyway For nested types This is something i personal do regulary. Felix K. Snake Snake 7, 6 6 gold badges 43 43 silver badges 68 68 bronze badges. NET there are two parts, one is the auto-generated code of a page and the other is the code you write.

The custom logic is written in the ". NET designer. For the same ASP. NET provides the ". So if you see any ASP. NET behind code class files it's marked by the word partial. So by using the partial keyword in ASP. NET the Microsoft team has made VS and developer work side by side thus not fiddling with each other's code and thus increasing productivity. So when you drag tables in these frameworks they create auto-generated classes as shown in the following figure.

In the following figure you can see how the auto-generated code has partial classes and partial method: The partial methods later can be extended for including custom logic.

For instance, you can see in the following code for the preceding auto-generated class "tblCustomer" we have used partial methods to override the "OnCustomerCodeChanged" event to ensure that the customer code is not more than 8 length.

Use number Better maintenance by compacting large classes The other important use of partial classes is for better maintenance of the project. If you have large classes with many methods as shown in the following figure, it's a bit of a pain to maintain those classes.

By using partial classes you can split them into physical files as shown in the following figure, thus improving your project and making it easier to maintain. Use number Multiple people working on the same class The last and final real time I see of partial classes is when we want two developers to work in the same class simultaneously.

I agree this can be a very rare use as there are better options like using a version control software like TFS or Subversion, but in case you want something quick and local this option is not bad at all. You can also watch my videos on various technologies like. View All.