【初心者向け】C#でイベント処理する10ステップ完全ガイド

private void button_Click(object sender, EventArgs e)
{
    MessageBox.Show("ボタンがクリックされました！");
}

using System;
using System.Windows.Forms;

public class MyForm : Form
{
    private Button myButton;

    public MyForm()
    {
        myButton = new Button();
        myButton.Text = "クリックしてください";
        myButton.Click += new EventHandler(this.button_Click);

        this.Controls.Add(myButton);
    }

    private void button_Click(object sender, EventArgs e)
    {
        MessageBox.Show("ボタンがクリックされました！");
    }

    static void Main()
    {
        Application.Run(new MyForm());
    }
}

using System;
using System.Windows.Forms;

public class TextInputForm : Form
{
    private TextBox textBox;
    private Button showButton;

    public TextInputForm()
    {
        textBox = new TextBox();
        showButton = new Button();

        showButton.Text = "表示";
        showButton.Click += new EventHandler(this.showButton_Click);

        textBox.Location = new System.Drawing.Point(10, 10);
        textBox.Width = 200;

        showButton.Location = new System.Drawing.Point(220, 10);

        this.Controls.Add(textBox);
        this.Controls.Add(showButton);
    }

    private void showButton_Click(object sender, EventArgs e)
    {
        MessageBox.Show(textBox.Text);
    }

    static void Main()
    {
        Application.Run(new TextInputForm());
    }
}

using System;

public class CustomEventArgs : EventArgs
{
    public string Message { get; set; }
}

public class Publisher
{
    public event EventHandler<CustomEventArgs> CustomEvent;

    public void RaiseCustomEvent(string message)
    {
        CustomEventArgs args = new CustomEventArgs() { Message = message };
        CustomEvent?.Invoke(this, args);
    }
}

public class Subscriber
{
    public void OnCustomEvent(object sender, CustomEventArgs e)
    {
        Console.WriteLine("イベントが発生しました: " + e.Message);
    }
}

class Program
{
    static void Main()
    {
        Publisher publisher = new Publisher();
        Subscriber subscriber = new Subscriber();

        publisher.CustomEvent += subscriber.OnCustomEvent;

        publisher.RaiseCustomEvent("Hello, world!");

        publisher.CustomEvent -= subscriber.OnCustomEvent;
    }
}

using System;
using System.Threading.Tasks;
using System.Windows.Forms;

public class AsyncForm : Form
{
    private Button fetchDataButton;

    public AsyncForm()
    {
        fetchDataButton = new Button();
        fetchDataButton.Text = "データ取得";
        fetchDataButton.Click += async (sender, e) => await FetchDataAsync();

        this.Controls.Add(fetchDataButton);
    }

    private async Task FetchDataAsync()
    {
        // 非同期でデータを取得する例
        await Task.Delay(1000); // 仮のデータ取得処理
        MessageBox.Show("データ取得完了！");
    }

    static void Main()
    {
        Application.Run(new AsyncForm());
    }
}

using System;
using System.Windows.Forms;

public class SimpleForm : Form
{
    private Button button;
    private TextBox textBox;

    public SimpleForm()
    {
        button = new Button
        {
            Text = "クリックしてください"
        };
        button.Click += Button_Click;

        textBox = new TextBox
        {
            Location = new System.Drawing.Point(10, 50),
            Width = 200
        };
        textBox.TextChanged += TextBox_TextChanged;

        this.Controls.Add(button);
        this.Controls.Add(textBox);
    }

    private void Button_Click(object sender, EventArgs e)
    {
        MessageBox.Show("ボタンがクリックされました！");
    }

    private void TextBox_TextChanged(object sender, EventArgs e)
    {
        Console.WriteLine("テキストが変更されました: " + textBox.Text);
    }

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

using System;
using System.Net.NetworkInformation;

class NetworkMonitor
{
    public void Start()
    {
        NetworkChange.NetworkAddressChanged += OnNetworkAddressChanged;
    }

    private void OnNetworkAddressChanged(object sender, EventArgs e)
    {
        Console.WriteLine("ネットワークの接続状態が変更されました。");
    }

    public void Stop()
    {
        NetworkChange.NetworkAddressChanged -= OnNetworkAddressChanged;
    }
}

class Program
{
    static void Main()
    {
        NetworkMonitor monitor = new NetworkMonitor();
        monitor.Start();

        Console.WriteLine("ネットワークの監視を開始しました。何かキーを押すと終了します。");
        Console.ReadKey();

        monitor.Stop();
    }
}

using System;

public class EventProcessor
{
    public event EventHandler MyEvent;

    public void Process()
    {
        try
        {
            // イベントの発火を試みる
            OnMyEvent();
        }
        catch (Exception ex)
        {
            Console.WriteLine("イベント処理中にエラーが発生しました: " + ex.Message);
            // 必要に応じてさらなるエラー処理を行う
        }
    }

    protected virtual void OnMyEvent()
    {
        MyEvent?.Invoke(this, EventArgs.Empty);
    }
}

class Program
{
    static void Main()
    {
        EventProcessor processor = new EventProcessor();
        processor.MyEvent += (sender, e) => { throw new InvalidOperationException("エラー発生"); };
        processor.Process();
    }
}

using System;

public class CustomEventArgs : EventArgs
{
    public int Value { get; set; }
}

public class CustomEventPublisher
{
    public event EventHandler<CustomEventArgs> CustomEvent;

    public void TriggerEvent(int value)
    {
        CustomEventArgs args = new CustomEventArgs { Value = value };
        CustomEvent?.Invoke(this, args);
    }
}

class Program
{
    static void Main()
    {
        CustomEventPublisher publisher = new CustomEventPublisher();
        publisher.CustomEvent += OnCustomEvent;

        publisher.TriggerEvent(10);
        publisher.TriggerEvent(20);
    }

    private static void OnCustomEvent(object sender, CustomEventArgs e)
    {
        Console.WriteLine($"イベントがトリガーされました。値: {e.Value}");
    }
}

// このコードはサンプルであり、実際のプロジェクトの具体的なコードを模範としています。
using System;
using System.Windows.Forms;
using System.Net.Sockets;

public class MyApp : Form
{
    private Button connectButton;
    private TcpClient tcpClient;
    private NetworkStream stream;

    public MyApp()
    {
        connectButton = new Button { Text = "接続" };
        connectButton.Click += ConnectButton_Click;
        Controls.Add(connectButton);
    }

    private void ConnectButton_Click(object sender, EventArgs e)
    {
        tcpClient = new TcpClient("サーバーアドレス", 1234);
        stream = tcpClient.GetStream();

        // ネットワークイベントの処理を追加
        stream.BeginRead(new byte[0], 0, 0, OnDataReceived, null);
    }

    private void OnDataReceived(IAsyncResult ar)
    {
        // データ受信時の処理
        Console.WriteLine("データが受信されました。");
    }

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

using System;
using System.Windows.Forms;
using System.Net.Http;
using System.Threading.Tasks;

public class DataFetchApp : Form
{
    private Button fetchDataButton;
    private Label dataDisplayLabel;
    private HttpClient httpClient;

    public DataFetchApp()
    {
        fetchDataButton = new Button { Text = "データ取得" };
        fetchDataButton.Click += FetchDataButton_Click;
        Controls.Add(fetchDataButton);

        dataDisplayLabel = new Label { AutoSize = true };
        Controls.Add(dataDisplayLabel);

        httpClient = new HttpClient();
    }

    private async void FetchDataButton_Click(object sender, EventArgs e)
    {
        string data = await FetchDataFromServer();
        dataDisplayLabel.Text = data;
    }

    private async Task<string> FetchDataFromServer()
    {
        HttpResponseMessage response = await httpClient.GetAsync("サーバーのURL");
        response.EnsureSuccessStatusCode();
        string responseBody = await response.Content.ReadAsStringAsync();
        return responseBody;
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new DataFetchApp());
    }
}