C# 2.0 除了泛型

/*
*可空类型    
*/
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

public partial class CSharp20_Nullable : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                // 针对值类型的可空类型
                Nullable<DateTime> dt = null;
                DateTime? dt2 = null;

                // ??分配默认值
                int? x = null;
                int y = x ?? -1;

                // x的默认值为0
                Response.Write(y.ToString());
        }
}

运行结果
-1

匿名方法

/*
* 匿名方法
*/
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

public partial class CSharp20_AnonymousMethod : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                Button btn = new Button();
                btn.Text = "按钮";
                // 一般方法
                btn.Click += new EventHandler(btn_Click);
                // 省略掉委托类型
                btn.Click += btn_Click2;
                // 不带参数的匿名方法
                btn.Click += delegate { Response.Write("按钮被单击（不带参数的匿名方法）<br />"); };
                // 带参数的匿名方法（参数数量和类型要一致）
                btn.Click += delegate(object obj, EventArgs er) { Response.Write("按钮被单击（带参数的匿名方法）<br />"); };

                Page.Form.Controls.Add(btn);
        }

        void btn_Click(object sender, EventArgs e)
        {
                Response.Write("按钮被单击<br />");
        }

        void btn_Click2(object sender, EventArgs e)
        {
                Response.Write("按钮被单击（省略掉委托类型）<br />");
        }
}

按了按钮后的运行结果
按钮被单击
按钮被单击（省略掉委托类型）
按钮被单击（不带参数的匿名方法）
按钮被单击（带参数的匿名方法）

迭代器

/*
* 迭代器
* 要实现foreach必须实现接口IEnumerable或者IEnumerator
*/
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

public class Charp20Yield
{
        public static IEnumerable YieldTest()
        {
                string[] ary = new string[] { "a", "b", "c", "d", "e", "f", "g" };

                foreach (string s in ary)
                {
                        if (s != "e")
                        {
                                // 产生枚举元素
                                yield return s;
                        }
                        else
                        {
                                // 中断迭代
                                yield break;
                        }
                }
        }
}


public partial class CSharp20_Iterator : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                // 使用自定义迭代器
                foreach (string s in Charp20Yield.YieldTest())
                {
                        Response.Write(s);
                        Response.Write("<br />");
                }
        }
}

运行结果
a
b
c
d

partial类

/*
* partial类
*/
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

// partial类可以写在不同的文件里，实际上就是取并集，类的修饰符要一致
public partial class PartialTest : IDisposable
{
        public string Get()
        {
                return "PartialTest";
        }
}

// partial类可以写在不同的文件里，实际上就是取并集，类的修饰符要一致
public partial class PartialTest
{
        public void Dispose()
        {
                // 略
        }
}


public partial class CSharp20_Partial : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                PartialTest pt = new PartialTest();
                Response.Write(pt.Get());
                pt.Dispose();
        }
}

运行结果
PartialTest

其它

/*
* 其它
*/
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

// 指定别名
using xyz = System.Text;

public partial class CSharp20_Other : System.Web.UI.Page
{
        protected void Page_Load(object sender, EventArgs e)
        {
                CSharp20_Other_Test c = new CSharp20_Other_Test();
                c.CurrentTime = DateTime.Now;

                // 下面这句会报错
                // Response.Write(c.CurrentTime.ToLongDateString());

                // 没问题，因为set是internal的
                c[2] = "insert";
                Response.Write(c[2]);
                Response.Write("<br />");

                // 自定义类与framework类 类名重复时，自定义类优先
                // xyz是命名空间别名
                // 访问全局的话用gloab
                Response.Write(xyz::Encoding.Default.EncodingName);
        }
}

public class CSharp20_Other_Test
{
        private DateTime _currentTime;
        public DateTime CurrentTime
        {
                // 给访问器增加修饰符
                // 如果接口定义访问器了，则所有继承的都是public
                protected get { return _currentTime; }
                set { _currentTime = value; }
        }

        private string[] ary = new string[] { "a", "b", "c", "d", "e", "f", "g" };
        public string this[int index]
        {
                get { return ary[index]; }
                // 给索引器增加修饰符
                internal set { ary[index] = value; }
        }
}

运行结果
insert
简体中文(GB2312)

OK
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