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C#入門二十五個代碼小例子

編輯：.NET實例教程

一、從控制台讀取東西代碼片斷：
using System;

class TestReadConsole
{
    public static void Main()
    {
        Console.Write(Enter your name:);
        string strName = Console.ReadLine();
        Console.WriteLine( Hi + strName);
    }
}

二、讀文件代碼片斷：
using System;
using System.IO;

public class TestReadFile
{
    public static void Main(String[] args)
    {
        // Read text file C: emp est.txt
        FileStream fs = new FileStream(@c: emp est.txt , FileMode.Open, FileAccess.Read);
        StreamReader sr = new StreamReader(fs);

        String line=sr.ReadLine();
        while (line!=null)
        {
            Console.WriteLine(line);
            line=sr.ReadLine();
        }

        sr.Close();
        fs.Close();
    }
}

三、寫文件代碼：
using System;
using System.IO;

public class TestWriteFile
{
    public static void Main(String[] args)
    {
        // Create a text file C: emp est.txt
        FileStream fs = new FileStream(@c: emp est.txt , FileMode.OpenOrCreate, FileAccess.Write);
        StreamWriter sw = new StreamWriter(fs);
        // Write to the file using StreamWriter class
        sw.BaseStream.Seek(0, SeekOrigin.End);
        sw.WriteLine( First Line );
        sw.WriteLine( Second Line);
        sw.Flush();
    }
}

$False$

四、拷貝文件：
using System;
using System.IO;

class TestCopyFile
{
    public static void Main()
    {
        File.Copy(c:\temp\source.txt, C:\temp\dest.txt );
    }
}

五、移動文件：
using System;
using System.IO;

class TestMoveFile
{
    public static void Main()
    {
        File.Move(c:\temp\abc.txt, C:\temp\def.txt );
    }
}

六、使用計時器：
using System;
using System.Timers;

class TestTimer
{
    public static void Main()
    {
        Timer timer = new Timer();

    timer.Elapsed += new ElapsedEventHandler( DisplayTimeEvent );
        timer.Interval = 1000;
        timer.Start();
        timer.Enabled = true;

        while ( Console.Read() != ''q'' )
        {
             //-------------
        }
    }
    public static void DisplayTimeEvent( object source, ElapsedEventArgs e )
    {
        Console.Write( {0}, DateTime.Now);
    }
}

七、調用外部程序：
class Test
{
    static void Main(string[] args)
    {
        System.Diagnostics.Process.Start(notepad.exe);
    }
}

ADO.Net方面的：
八、連接Access數據庫：
using System;
using System.Data;
using System.Data.OleDb;

class TestADO
{
    static void Main(string[] args)
    {
        string strDSN = Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\test.mdb;
        string strSQL = SELECT * FROM employees ;

        OleDbConnection conn = new OleDbConnection(strDSN);
        OleDbCommand cmd = new OleDbCommand( strSQL, conn );
        OleDbDataReader reader = null;
        try
        {
            conn.Open();
            reader = cmd.ExecuteReader();
            while (reader.Read() )
            {
                Console.WriteLine(First Name:{0}, Last Name:{1}, reader[FirstName], reader[LastName]);
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            conn.Close();
        }
    }
}

九、連接SQL Server數據庫：
using System;
using System.Data.SqlClIEnt;

public class TestADO
{
    public static void Main()
    {
        SqlConnection conn = new SqlConnection(Data Source=localhost; Integrated Security=SSPI; Initial Catalog=pubs);

SqlCommand  cmd = new SqlCommand(SELECT * FROM employees, conn);
        try
        {
            conn.Open();

            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                Console.WriteLine(First Name: {0}, Last Name: {1}, reader.GetString(0), reader.GetString(1));
            }

            reader.Close();
            conn.Close();
        }
        catch(Exception e)
        {
            Console.WriteLine(Exception Occured -->> {0},e);
        }
    }
}

十、從SQL內讀數據到XML：
using System;
using System.Data;
using System.XML;
using System.Data.SqlClIEnt;
using System.IO;

public class TestWriteXML
{
    public static void Main()
    {

        String strFileName=c:/temp/output.XML;

        SqlConnection conn = new SqlConnection(server=localhost;uid=sa;pwd=;database=db);

        String strSql = SELECT FirstName, LastName FROM employees;

        SqlDataAdapter adapter = new SqlDataAdapter();

        adapter.SelectCommand = new SqlCommand(strSql,conn);

        // Build the DataSet
        DataSet ds = new DataSet();

        adapter.Fill(ds, employees);

        // Get a FileStream object
        FileStream fs = new FileStream(strFileName,FileMode.OpenOrCreate,FileAccess.Write);

        // Apply the WriteXml method to write an XML document
        ds.WriteXML(fs);

        fs.Close();

    }
}

十一、用ADO添加數據到數據庫中：
using System;
using System.Data;
using System.Data.OleDb;

class TestADO
{
    static void Main(string[] args)

{
        string strDSN = Provider=Microsoft.Jet.OLEDB.4.0;DataSource=c: est.mdb;
        string strSQL = INSERT INTO Employee(FirstName, LastName) VALUES(''FirstName'', ''LastName'') ;

        // create Objects of ADOConnection and ADOCommand
        OleDbConnection conn = new OleDbConnection(strDSN);
        OleDbCommand cmd = new OleDbCommand( strSQL, conn );
        try
        {
            conn.Open();
            cmd.ExecuteNonQuery();
        }
        catch (Exception e)
        {
            Console.WriteLine(Oooops. I did it again: {0}, e.Message);
        }
        finally
        {
            conn.Close();
        }
    }
}

十二、使用OLEConn連接數據庫：
using System;
using System.Data;
using System.Data.OleDb;

class TestADO
{
    static void Main(string[] args)
    {
        string strDSN = Provider=Microsoft.Jet.OLEDB.4.0;DataSource=c: est.mdb;
        string strSQL = SELECT * FROM employee ;

        OleDbConnection conn = new OleDbConnection(strDSN);
        OleDbDataAdapter cmd = new OleDbDataAdapter( strSQL, conn );

        conn.Open();
        DataSet ds = new DataSet();
        cmd.Fill( ds, employee );
        DataTable dt = ds.Tables[0];

        foreach( DataRow dr in dt.Rows )
        {
            Console.WriteLine(First name: + dr[FirstName].ToString() + Last name: + dr[LastName].ToString());
        }
        conn.Close();
    }
}
十三、讀取表的屬性：

using System;
using System.Data;
using System.Data.OleDb;

class TestADO
{
    static void Main(string[] args)
    {
        string strDSN = Provider=Microsoft.Jet.OLEDB.4.0;DataSource=c: est.mdb;
        string strSQL = SELECT * FROM employee ;

        OleDbConnection conn = new OleDbConnection(strDSN);
        OleDbDataAdapter cmd = new OleDbDataAdapter( strSQL, conn );

        conn.Open();
        DataSet ds = new DataSet();
        cmd.Fill( ds, employee );
        DataTable dt = ds.Tables[0];

        Console.WriteLine(FIEld Name DataType Unique AutoIncrement AllowNull);
        Console.WriteLine(==================================================================);
        foreach( DataColumn dc in dt.Columns )
        {
            Console.WriteLine(dc.ColumnName+ , +dc.DataType + ,+dc.Unique + ,+dc.AutoIncrement+ ,+dc.AllowDBNull );
        }
        conn.Close();
    }
}

ASP.Net方面的
十四、一個ASP.Net程序：
<%@ Page Language=C# %>
<script runat=server>

    void Button1_Click(Object sender, EventArgs e)
    {
        Label1.Text=TextBox1.Text;
    }

</script>
<Html>
<head>
</head>
<body>
    <form runat=server>
        <p>
            <br />
            Enter your name: <asp:TextBox id=TextBox1 runat=server></ASP:TextBox>
        </p>
        <p>
            <b><asp:Label id=Label1 runat=server Width=247px></ASP:Label></b>
        </p>
        <p>
            <asp:Button id=Button1 onclick=Button1_Click runat=server Text=Submit></ASP:Button>
        </p>
    </form>
</body>
</Html>

WinForm開發：
十五、一個簡單的WinForm程序：
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

public class SimpleForm : System.Windows.Forms.Form
{

    private System.ComponentModel.Container components = null;
    private System.Windows.Forms.Button button1;
    private System.Windows.Forms.TextBox textBox1;
    public SimpleForm()
    {
        InitializeComponent();
    }

    protected override void Dispose( bool disposing )
    {
        if( disposing )
        {
            if (components != null)
            {
                components.Dispose();
            }
        }
        base.Dispose( disposing );
    }

    #region Windows Form Designer generated code
    private void InitializeComponent()
    {

        this.components = new System.ComponentModel.Container();
        this.Size = new System.Drawing.Size(300,300);
        this.Text = Form1;

        this.button1 = new System.Windows.Forms.Button();
        this.textBox1 = new System.Windows.Forms.TextBox();
        this.SuspendLayout();

//
    // button1
    //

    this.button1.Location = new System.Drawing.Point(8, 16);
    this.button1.Name = button1;
    this.button1.Size = new System.Drawing.Size(80, 24);
    this.butto, n1.TabIndex = 0;
    this.button1.Text = button1;

    //
    // textBox1
    //
    this.textBox1.Location = new System.Drawing.Point(112, 16);
    this.textBox1.Name = textBox1;
    this.textBox1.Size = new System.Drawing.Size(160, 20);
    this.textBox1.TabIndex = 1;
    this.textBox1.Text = textBox1;
    //
    // Form1
    //

this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
    this.ClIEntSize = new System.Drawing.Size(292, 273);
    this.Controls.AddRange(new System.Windows.Forms.Control[] {
    this.textBox1,
    this.button1});
    this.Name = Form1;
    this.Text = Form1;
    this.ResumeLayout(false);

    }
    #endregion

    [STAThread]

    static void Main()
    {
        Application.Run(new SimpleForm());
    }
}
十六、運行時顯示自己定義的圖標：
//load icon and set to form
System.Drawing.Icon ico = new System.Drawing.Icon(@c: empapp.ico);
this.Icon = ico;
十七、添加組件到ListBox中：
private void Form1_Load(object sender, System.EventArgs e)
{
    string str = First item;
    int i = 23;
    float flt = 34.98f;
    listBox1.Items.Add(str);
    listBox1.Items.Add(i.ToString());
    listBox1.Items.Add(flt.ToString());
    listBox1.Items.Add(Last Item in the List Box);
}

網絡方面的：
十八、取得IP地址：
using System;
using System.Net;

class GetIP
{
     public static void Main()
     {
         IPHostEntry ipEntry = Dns.GetHostByName (localhost);
         IPAddress [] IpAddr = ipEntry.AddressList;
         for (int i = 0; i < IpAddr.Length; i++)
         {
             Console.WriteLine (IP Address {0}: {1} , i, IpAddr.ToString ());
         }
    }
}
十九、取得機器名稱：
using System;
using System.Net;

class GetIP
{
    public static void Main()
    {
          Console.WriteLine (Host name : {0}, Dns.GetHostName());
    }
}

二十、發送郵件：
using System;
using System.Web;
using System.Web.Mail;

public class TestSendMail
{
    public static void Main()
    {
        try
        {
            // Construct a new mail message
            MailMessage message = new MailMessage();
            message.From = [email protected];
            message.To   =  [email protected];
            message.Cc   = ;
            message.Bcc  = ;
            message.Subject = Subject;
            message.Body = Content of message;

            //if you want attach file with this mail, add the line below
            message.Attachments.Add(new MailAttachment(c:\attach.txt, MailEncoding.Base64));

            // Send the message
            SmtpMail.Send(message);
            System.Console.WriteLine(Message has been sent);
        }

        catch(Exception ex)
        {
            System.Console.WriteLine(ex.Message.ToString());
        }

    }
}
二

十一、根據IP地址得出機器名稱：
using System;
using System.Net;

class ResolveIP
{
     public static void Main()
     {
         IPHostEntry ipEntr.Resolve(172.29.9.9);
         Console.WriteLine (Host name : {0}, ipEntry.HostName);
     }
}

GDI+方面的：
二十二、GDI+入門介紹：
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

public class Form1 : System.Windows.Forms.Form
{
    private System.ComponentModel.Container components = null;

    public Form1()
    {
        InitializeComponent();
    }

    protected override void Dispose( bool disposing )
    {
        if( disposing )
        {
            if (components != null)
            {
                components.Dispose();
            }
        }
        base.Dispose( disposing );
    }

    #region Windows Form Designer generated code
    private void InitializeComponent()
    {
        this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
        this.ClIEntSize = new System.Drawing.Size(292, 273);
        this.Name = Form1;
        this.Text = Form1;
        this.Paint += new System.Windows.Forms.PaintEventHandler(this.Form1_Paint);
    }
    #endregion

    [STAThread]
    static void Main()
    {
        Application.Run(new Form1());
    }

    private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
    {
        Graphics g=e.Graphics;
        g.DrawLine(new Pen(Color.Blue),10,10,210,110);
        g.DrawRectangle(new Pen(Color.Red),10,10,200,100);
        g.DrawEllipse(new Pen(Color.Yellow),10,150,200,100);
    }
}

XML方面的：

二十三、讀取XML文件：
using System;
using System.XML;

class TestReadXML
{
    public static void Main()
    {

        XmlTextReader reader  = new XmlTextReader(C:\test.XML);
        reader.Read();

        while (reader.Read())
        {
            reader.MoveToElement();
            Console.WriteLine(XMLTextReader PropertIEs Test);
            Console.WriteLine(===================);

            // Read this propertIEs of element and display them on console
            Console.WriteLine(Name: + reader.Name);
            Console.WriteLine(Base URI: + reader.BaseURI);
            Console.WriteLine(Local Name: + reader.LocalName);
            Console.WriteLine(Attribute Count: + reader.AttributeCount.ToString());
            Console.WriteLine(Depth: + reader.Depth.ToString());
            Console.WriteLine(Line Number: + reader.LineNumber.ToString());
            Console.WriteLine(Node Type: + reader.NodeType.ToString());
            Console.WriteLine(Attribute Count: + reader.Value.ToString());
        }
    }
}
二十四、寫XML文件：
using System;
using System.XML;

public class TestWriteXMLFile
{
    public static int Main(string[] args)
    {
        try
        {
            // Creates an XML file is not exist
            XmlTextWriter writer = new XmlTextWriter(C:\temp\xmltest.XML, null);

           // Starts a new document
            writer.WriteStartDocument();
            //Write comments
            writer.WriteComment(Commentss: XMLWriter Test Program);
            writer.WriteProcessingInstruction(Instruction,Person Record);
            // Add elements to the file
            writer.WriteStartElement(p, person, urn:person);
            writer.WriteStartElement(LastName,);
            writer.WriteString(Chand);
            writer.WriteEndElement();
            writer.WriteStartElement(FirstName,);
            writer.WriteString(Mahesh);
            writer.WriteEndElement();
            writer.WriteElementInt16(age,, 25);
            // Ends the document
            writer.WriteEndDocument();
        }
        catch (Exception e)
        {
            Console.WriteLine (Exception: {0}, e.ToString());
        }
        return 0;
    }
}

Web Service方面的：
二十五、一個Web Service的小例子：
<% @WebService Language=C# Class=TestWS %>

using System.Web.Services;

public class TestWS : System.Web.Services.WebService
{
    [WebMethod()]
    public string StringFromWebService()
    {
        return This is a string from web service.;
    }
}