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步步为营VS 2008 + .NET 3.5(3) - C# 3.0新特性之Automatic Properties（自动属性）、Object Initializers（对象初始化器）、Collection Initializers（集合初始化器）和Extension Methods（扩展方法）


作者： webabcd


介绍
    ·Automatic Properties（自动属性）
    ·Object Initializers（对象初始化器）
    ·Collection Initializers（集合初始化器）
    ·Extension Methods（扩展方法）


示例
AutomaticProperties.cs（自动属性）
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;

///
/// AutomaticProperties（自动属性）的摘要说明
///
public class AutomaticProperties
{
         public int ID { get; set; }

         // 上面的ID属性（自动属性）等同于下面的ID属性

         // private int _id;
         // public int ID
         // {
         //         get { return _id; }
         //         set { _id = value; }
         // }
}
 
ObjectInitializers.cs（对象初始化器）
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;

///
/// ObjectInitializers（对象初始化器）的摘要说明
///
public class ObjectInitializers
{
         public int ID { get; set; }
         public string Name { get; set; }

         public void ObjectInitializersTest()
        {
                ObjectInitializers oi = new ObjectInitializers { ID = 1, Name = "webabcd" };

                 // 上面的oi对象（对象初始化器）等同于下面的oi对象

                 // ObjectInitializers oi = new ObjectInitializers();
                 // oi.ID = 1;
                 // oi.Name = "webabcd";
        }
}
 
CollectionInitializers.cs（集合初始化器）
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;

using System.Collections.Generic;

///
/// CollectionInitializers（集合初始化器）的摘要说明
///
public class CollectionInitializers
{
         public int ID { get; set; }
         public string Name { get; set; }

         public void CollectionInitializersTest()
        {
                List list = new List
                {
                         new CollectionInitializers { ID = 1, Name = "webabcd" },
                         new CollectionInitializers { ID = 2, Name = "webabcdefg" },
                         new CollectionInitializers { ID = 3, Name = "webabcdefghijklmn" }
                };

                 // 上面的list集合（集合初始化器）等同于下面的list集合

                 // List list = new List();
                 // list.Add(new CollectionInitializers { ID = 1, Name = "webabcd" });
                 // list.Add(new CollectionInitializers { ID = 2, Name = "webabcdefg" });
                 // list.Add(new CollectionInitializers { ID = 3, Name = "webabcdefghijklmn" });
        }
}
 
ExtensionMethods.cs（扩展方法）
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;

///
/// ExtensionMethods 的摘要说明
///
public class ExtensionMethods
{
         public void ExtensionMethodsTest()
        {
                 string s = "123";
                 // 使用string的ToInt32()扩展方法
                 int i = s.ToInt32();
                 // i == 123

                 string[] ary = new string[] { "a", "b", "c" };
                 // 使用object的In()扩展方法
                 bool b = "b".In(ary);
                 // b == true
        }
}

///
/// 扩展方法（类和方法均为static）
/// 使用的时候要引用该类的命名空间
///
public static class MyExtensionMethods
{
         // this代表扩展方法应用于string类型上
         // ToInt32()是将string类型转换为int类型的扩展方法
         public static int ToInt32( this string s)
        {
                 int i;
                Int32.TryParse(s, out i);

                 return i;
        }

         // this代表扩展方法应用于object类型上
         // 该扩展方法需要一个类型为System.Collections.IEnumerable的参数
         // In()是判断一个object是否存在于一个System.Collections.IEnumerable中的扩展方法
         public static bool In( this object o, System.Collections.IEnumerable e)
        {
                 foreach ( object i in e)
                {
                         if (i.Equals(o))
                        {
                                 return true;
                        }
                }

                 return false;
        }
}
 
 
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