C# delegate委托五步法学习笔记，带参数和返回值

步骤

1.声明委托
2.创建委托对象
3.创建委托方法
4.绑定委托
5.调用委托

界面

主窗体代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    // 1.声明委托（在命名空间）
    public delegate void A_delegate(string value);
    public delegate void B_delegate(string value1, string value2, string value3);
    public delegate string C_delegate(string value);
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Form2 frm2 = new Form2();
            // 4.绑定委托
            frm2.setvalue_A1 += this.Setvalue1;
            frm2.setvalue_A2 += this.Setvalue2;
            frm2.setvalue_B += this.Setvalue3;
            frm2.setvalue_C += this.Getvalue;
            frm2.Show();
        }
        // 3.创建委托方法
        public void Setvalue1(string value)
        {
            textBox1.Text = value;
        }
        public void Setvalue2(string value)
        {
            textBox2.Text = value;
        }
        public void Setvalue3(string value1, string value2, string value3)
        {
            textBox3.Text = value1 + value2 + value3;
        }
        public string Getvalue(string value)
        {
            return "C：" + value;
        }
    }
}

子窗体代码

using System;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }
        // 2.创建委托对象
        public A_delegate setvalue_A1;
        public A_delegate setvalue_A2;
        public B_delegate setvalue_B;
        public C_delegate setvalue_C;

        private void button1_Click(object sender, EventArgs e)
        {
            // 5.调用委托
            setvalue_A1?.Invoke(textBox1?.Text);
            setvalue_A2?.Invoke(textBox2?.Text);
            setvalue_B?.Invoke(textBox1?.Text, textBox2?.Text, textBox3?.Text);
            textBox4.Text = setvalue_C?.Invoke(textBox1.Text);
        }
    }
}