C# in Depth Third Edition 学习笔记-- C#2的一些特性

1. Partial class: 可以在多个源文件中写一个类。特别适合部分代码自动生成，部分代码手动添加的特性。

    编译器在编译前会把所有的源文件合并到意洽。但是一个方法不能在一个文件中开始，在另一个文件中结束。

       C#3中独有的pratial 方法：

// Generated.cs
using System;
partial class PartialMethodDemo
{
public PartialMethodDemo()
{
OnConstructorStart();
Console.WriteLine("Generated constructor");
OnConstructorEnd();
}
partial void OnConstructorStart();
partial void OnConstructorEnd();
}


using System;
partial class PartialMethodDemo
{
partial void OnConstructorEnd()
{
Console.WriteLine("Manual code");
}
}

2. 静态类型static classes

3. 独立的取值方法/赋值属性访问器separate getter/setter property access

     

string name;
public string Name
{
get { return name; }
private set
{
// Validation, logging etc here
name = value;
}
}

4. 命名空间别名Namespace aliases

using System;
using WinForms = System.Windows.Forms;
using WebForms = System.Web.UI.WebControls;
class Test
{
static void Main()
{
Console.WriteLine(typeof(WinForms.Button));
Console.WriteLine(typeof(WebForms.Button));
}
}

　　C#2 告知编译器使用别名

using System;
using WinForms = System.Windows.Forms;
using WebForms = System.Web.UI.WebControls;
class WinForms {}
class Test
{
static void Main()
{
Console.WriteLine(typeof(WinForms::Button));
Console.WriteLine(typeof(WebForms::Button));
}
}

　　全局命名空间别名

using System;
class Configuration {}
namespace Chapter7
{
class Configuration {}
class Test
{
static void Main()
{
Console.WriteLine(typeof(Configuration));
Console.WriteLine(typeof(global::Configuration));
Console.WriteLine(typeof(global::Chapter7.Test));
}
}
}

　　外部别名

// Compile with
// csc Test.cs /r:FirstAlias=First.dll /r:SecondAlias=Second.dll
extern alias FirstAlias;
extern alias SecondAlias;
using System;
using FD = FirstAlias::Demo;
class Test
{
static void Main()
{
Console.WriteLine(typeof(FD.Example));
Console.WriteLine(typeof(SecondAlias::Demo.Example));
}
}

5. pragma directives

    禁用和恢复警告CS0169

    　

public class FieldUsedOnlyByReflection
{
int x;
}
If you try to compile listing 7.9, you’ll get a warning message like this:
FieldUsedOnlyByReflection.cs(3,9): warning CS0169:
The private field 'FieldUsedOnlyByReflection.x' is never used

　　

public class FieldUsedOnlyByReflection
{
#pragma warning disable 0169
int x;
#pragma warning restore 0169
}

　　Checksum pragmas

#pragma checksum "filename" "{guid}" "checksum bytes"

6. 非安全代码中的固定大小的缓冲区Fixed-size buffers in unsafe code

7. 把内部成员暴露给选定的程序集

   简单情况下的友元程序集

   

// Compiled to Source.dll
using System.Runtime.CompilerServices;
[assembly:InternalsVisibleTo("FriendAssembly")]
public class Source
{
internal static void InternalMethod() {}
public static void PublicMethod() {}
}
// Compiled to FriendAssembly.dll
public class Friend
{
static void Main()
{
Source.InternalMethod();
Source.PublicMethod();
}
}
// Compiled to EnemyAssembly.dll
public class Enemy
{
static void Main()
{
// Source.InternalMethod();
Source.PublicMethod();
}
}