C# Callback思維

方式一、用委托作為形參，把結果傳回實參
方式二、通過接口實現
方式三、通過事件關聯，適用桌面應用程序
方式四、子窗體調用父窗體的函數(委托)

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方式一、用委托作為形參，把結果傳回實參

public partial class index : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Child chld = new Child();
        chld.GetURL((url) =>
        {
            Response.Write(url);
            //取得結果：http://microsoft-zh.cn
        });
    }
}
public class Child
{
    //創建委托
    public delegate void GetURLDelegate(string url);
    public void GetURL(GetURLDelegate func)
    {
        func("http://microsoft-zh.cn");
    }
}

 方式二、通過接口實現

public partial class index : System.Web.UI.Page, ILoginCallback
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Child chld = new Child();
        chld.GetURL(this);
    }
    public void OnGetURL(string url)
    {
        Response.Write(url);
        //取得結果：http://microsoft-zh.cn
    }
}
public class Child
{
    public void GetURL(ILoginCallback callback)
    {
        callback.OnGetURL("http://microsoft-zh.cn");
    }
}

public interface ILoginCallback
{
    /// <summary>
    /// 接口函數
    /// </summary>
    void OnGetURL(string url);
}

方式三、通過事件關聯，適用桌面應用程序

public partial class Form1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    Form2 chld = new Form2();
    protected void Button1_Click(object sender, EventArgs e)
    {
        chld.AuthReady += new AuthEventHandler(chld.OnAuthReady);
    }
}
public partial class Form2 : System.Web.UI.Page
{
    // 事件
    public event AuthEventHandler AuthReady;
    protected void Button2_Click(object sender, EventArgs e)
    {
        if (AuthReady != null)
        {
            AuthEventArgs args = new AuthEventArgs();
            args.user_id = 1;
            args.user_name = "micro";
            AuthReady(this, args);
        }
    }
    public void OnAuthReady(object sender, AuthEventArgs e)
    {
        Console.Write(e.user_name);
    }
}
//委托事件
public delegate void AuthEventHandler(object sender, AuthEventArgs e);
public class AuthEventArgs : EventArgs
{
    public int user_id { get; set; }
    public string user_name { get; set; }
}

方式四、子窗體調用父窗體的函數(委托)
1、子窗體Form2


public partial class Form2 : Form
{
    // 申明委托，與父窗體方法類型相同
    public delegate string FunDelegate(int a);
    // 用來接收父窗體方法的委托變量
    public FunDelegate funDelegate;
    private void button1_Click(object sender, EventArgs e)
    {
        if (funDelegate != null)
        {
            // 調用方法
            funDelegate(2);
        }
    }
}

 2、父窗體Form1

private void Form1_Load(object sender, EventArgs e)
{
    Form2 frm2 = new Form2();
    //父窗體的方法傳給子窗體
    frm2.FunDelegate = Fun; 
    frm2.Show();
}
// 父窗體的方法
private string Fun(int a)
{
    return "我是主窗體方法";
}