每当我有一个类，其中包含一个具有重要大小/复杂性的嵌套类时，我将该类标记为partial，并将嵌套类放在一个单独的文件中。我使用规则命名包含嵌套类的文件:[class name]。[嵌套类名].cs。

下面的MSDN博客解释了如何使用带有嵌套类的部分类来实现可维护性:http://blogs.msdn.com/b/marcelolr/archive/2009/04/13/using-partial-classes-with-nested-classes-for-maintainability.aspx

一个很好的用法是将生成的代码与属于同一类的手写代码分离。

例如，由于LINQ to SQL使用部分类，您可以编写自己的某些功能片段的实现(如多对多关系)，并且当您重新生成代码时，这些自定义代码片段不会被覆盖。

WinForms代码也是如此。所有设计器生成的代码都放在一个文件中，您通常不会接触这个文件。手写的代码放到另一个文件中。这样，当您在设计器中更改某些内容时，您所做的更改不会被影响。

Multiple Developer Using Partial Classes multiple developer can work on the same class easily. Code Generator Partial classes are mainly used by code generator to keep different concerns separate Partial Methods Using Partial Classes you can also define Partial methods as well where a developer can simply define the method and the other developer can implement that. Partial Method Declaration only Even the code get compiled with method declaration only and if the implementation of the method isn't present compiler can safely remove that piece of code and no compile time error will occur. To verify point 4. Just create a winform project and include this line after the Form1 Constructor and try to compile the code partial void Ontest(string s);

以下是在实现分部类时需要考虑的几点

Use partial keyword in each part of partial class. The name of each part of partial class should be the same but the 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 from a different class library project. Each part of a partial class must have the same accessibility. (i.e: private, public or protected) If you inherit a class or interface on a partial class then it is inherited by all parts of that 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 considered an abstract class.

我发现令人不安的是，“凝聚力”这个词在这些帖子中没有出现(直到现在)。 我也很不安，有人认为启用或鼓励大型类和方法在某种程度上是件好事。 如果你试图理解和维护代码基础的“部分”，那就糟透了。

分部类的主要用途是生成代码。如果你看看WPF (Windows Presentation Foundation)网络，你用标记(XML)定义你的UI。该标记被编译成部分类。您可以用自己的部分类填充代码。

的确，Partial Class用于自动代码生成，其中一个用途是维护一个可能有上千行代码的大型类文件。你永远不知道你的类最终会有1万行，你不想用不同的名字创建一个新类。

public partial class Product
{
    // 50 business logic embedded in methods and properties..
}

public partial class Product
{
    // another 50 business logic embedded in methods and properties..
}
//finally compile with product.class file.

另一个可能的用途是多个开发人员可以使用同一个类，因为它们存储在不同的地方。人们可能会笑，但你永远不知道有时候情况会很棘手。

Product1.cs

public partial class Product
{
    //you are writing the business logic for fast moving product
}

Product2.cs

public partial class Product
{
    // Another developer writing some business logic...
}

希望这是有意义的!