C# 入門代碼大全：控制台、文件、ADO.NET、ASP.NET、WinForms、網絡、GDI+、XML、Web Service

基礎輸入輸出

控制台讀寫

Console.Write("Enter name: ");
string name = Console.ReadLine();
Console.WriteLine($"Hi {name}");

文件讀取

using (FileStream fs = new FileStream(@"c:\temp\test.txt", FileMode.Open, FileAccess.Read))
using (StreamReader sr = new StreamReader(fs))
{
    string line;
    while ((line = sr.ReadLine()) != null)
        Console.WriteLine(line);
}

文件寫入

using (FileStream fs = new FileStream(@"c:\temp\test.txt", FileMode.OpenOrCreate, FileAccess.Write))
using (StreamWriter sw = new StreamWriter(fs))
{
    sw.BaseStream.Seek(0, SeekOrigin.End);
    sw.WriteLine("First Line");
    sw.WriteLine("Second Line");
}

文件複製/移動

File.Copy(@"c:\temp\source.txt", @"c:\temp\dest.txt");
File.Move(@"c:\temp\abc.txt", @"c:\temp\def.txt");

計時器與外部進程

// Timer
var timer = new System.Timers.Timer(1000);
timer.Elapsed += (s, e) => Console.Write($"\r{DateTime.Now}");
timer.Start();

// 啟動外部程序
Process.Start("notepad.exe");

ADO.NET 數據訪問

Access (OleDb)

string connStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\\test.mdb";
using (var conn = new OleDbConnection(connStr))
using (var cmd = new OleDbCommand("SELECT * FROM employees", conn))
{
    conn.Open();
    using (var reader = cmd.ExecuteReader())
        while (reader.Read())
            Console.WriteLine($"{reader["FirstName"]} {reader["LastName"]}");
}

SQL Server (SqlClient)

using (var conn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=pubs"))
using (var cmd = new SqlCommand("SELECT * FROM employees", conn))
{
    conn.Open();
    using (var reader = cmd.ExecuteReader())
        while (reader.Read())
            Console.WriteLine($"{reader.GetString(0)} {reader.GetString(1)}");
}

DataSet 填充與寫 XML

var adapter = new SqlDataAdapter("SELECT * FROM employees", conn);
var ds = new DataSet();
adapter.Fill(ds, "employees");
ds.WriteXml(@"c:\temp\output.xml");

ASP.NET 頁面示例

<%@ Page Language="C#" %>



    
    
    

WinForms 基礎模板

public class SimpleForm : Form
{
    private Button button1;
    private TextBox textBox1;

    public SimpleForm() { InitializeComponent(); }

    private void InitializeComponent()
    {
        this.button1 = new Button { Location = new Point(8,16), Text = "Click" };
        this.textBox1 = new TextBox { Location = new Point(112,16), Text = "Hello" };
        this.Controls.AddRange(new Control[] { this.textBox1, this.button1 });
        this.Text = "Demo";
    }

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

網絡編程

獲取本機 IP

IPHostEntry entry = Dns.GetHostEntry("localhost");
foreach (IPAddress ip in entry.AddressList)
    Console.WriteLine(ip);

Socket HTTP GET

var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
socket.Connect(new IPEndPoint(Dns.GetHostAddresses("example.com")[0], 80));
socket.Send(Encoding.ASCII.GetBytes("GET / HTTP/1.1\r\nHost: example.com\r\nConnection: Close\r\n\r\n"));
// 接收循環...

發送郵件

var msg = new MailMessage
{
    From = "from@domain.com",
    To = "to@domain.com",
    Subject = "Test",
    Body = "Content"
};
SmtpMail.Send(msg);

GDI+ 繪圖

private void Form1_Paint(object sender, 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 讀寫

XmlTextReader 讀取

using (var reader = new XmlTextReader("test.xml"))
{
    while (reader.Read())
    {
        reader.MoveToElement();
        Console.WriteLine($"Name:{reader.Name}, Value:{reader.Value}");
    }
}

XmlTextWriter 寫入

using (var writer = new XmlTextWriter("output.xml", null))
{
    writer.WriteStartDocument();
    writer.WriteStartElement("person");
    writer.WriteElementString("FirstName", "John");
    writer.WriteElementString("LastName", "Doe");
    writer.WriteEndElement();
    writer.WriteEndDocument();
}

Web Service (ASMX)

<%@ WebService Language="C#" Class="TestWS" %>
using System.Web.Services;

public class TestWS : WebService
{
    [WebMethod]
    public string Hello() => "Hello from Web Service!";
}