一、从控制台读取东西代码片断：
using System;

class TestReadConsole
{
public static void Main()
{
Console.Write(Enter your name:);
string strName = Console.ReadLine();
Console.WriteLine( Hi + strName);
}
}
二、读文件代码片断：
using System;
using System.IO;

public class TestReadFile
{
public static void Main(String[] args)
{
// Read text file C:\temp\test.txt
FileStream fs = new FileStream(@c:\temp\test.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、写文件代码：
using System;
using System.IO;

public class TestWriteFile
{
public static void Main(String[] args)
{
// Create a text file C:\temp\test.txt
FileStream fs = new FileStream(@c:\temp\test.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();
}
}
四、拷贝文件：
using System;
using System.IO;

class TestCopyFile
{
public static void Main()
{
File.Copy(c:\\temp\\source.txt, C:\\temp\\dest.txt );
}
}
五、移动文件：
using System;
using System.IO;

class TestMoveFile
{
public static void Main()
{
File.Move(c:\\temp\\abc.txt, C:\\temp\\def.txt );
}
}
六、使用计时器：
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(\\r{0}, DateTime.Now);  
}  

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

ADO.NET方面的：
八、连接Access数据库：
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、连接SQL Server数据库：
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、从SQL内读数据到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添加数据到数据库中：
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:\test.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:\\n{0}, e.Message);  
    }  
    finally  
    {  
        conn.Close();  
    }  
}  

}
十二、使用OLEConn连接数据库：
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:\test.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、读取表的属性：
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:\test.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、一个ASP.NET程序：
<%@ Page Language=C# %>

Enter your name:

WinForm开发：
十五、一个简单的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.button1.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、运行时显示自己定义的图标：
//load icon and set to form
System.Drawing.Icon ico = new System.Drawing.Icon(@c:\temp\app.ico);
this.Icon = ico;
十七、添加组件到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);
}

网络方面的：
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、取得机器名称：
using System;
using System.Net;

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