C#(Winfrom)窗体传值问题(子窗体回传值给父窗体)

Posted 2023-05-05

运行后，点击Form1的button1 调出Form2，点击Form2的Button1，关闭Form2，同时form2上的Textbox中的值复制到Form1中的Textbox1中。
代码如下form1
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication5数据传输单向

public partial class Form1 : Form

public Form1()

InitializeComponent();

private string a;
public Form1(string a)

this.a = a;
InitializeComponent();


private void Form1_Load(object sender, EventArgs e)

this.textBox1.Text = a;


private void button1_Click(object sender, EventArgs e)

Form Form30 = new Form2();

Form30.TopLevel = false;
Form30.Parent = panel1;
//Form2.BackColor = Color.Black;
Form30.Size = panel1.Size;
Form30.Anchor = AnchorStyles.Left | AnchorStyles.Right | AnchorStyles.Top | AnchorStyles.Bottom;
Form30.Show();





form2
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication5数据传输单向

public partial class Form2 : Form

public Form2()

InitializeComponent();


private void button1_Click(object sender, EventArgs e)

Form1 frm1 = (Form1)this.Owner;
frm1.textBox1.Text = this.textBox1.Text;
this.Close();




可是运行时总是弹出“未处理的“System.NullReferenceException”类型的异常出现在 WindowsFormsApplication5数据传输单向.exe 中。

其他信息: 未将对象引用设置到对象的实例。”请问这是怎么回事儿？

参考技术A 实现思路：在子窗体定义委托 父窗体接收 参考技术B using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication5数据传输单向

public partial class Form1 : Form

public Form1()

InitializeComponent();

public void a(Form2 f2)

this.textBox1.Text = f2.a;

private void button1_Click_1(object sender, EventArgs e)

Form2 f2 = new Form2();
f2.f1 = this;
f2.Show();





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

namespace WindowsFormsApplication5数据传输单向

public partial class Form2 : Form

public Form1 f1;
internal string a;
public Form2()

InitializeComponent();

private void button1_Click_1(object sender, EventArgs e)

f1.a(this);
f1.Show();
this.Close();


private void Form2_Load(object sender, EventArgs e)


a = this.textBox1.Text;


本回答被提问者采纳

c# 不同窗体之间传值和调用

1.子窗体事件刷新父窗体界面值

   子窗体定义委托和事件  

 //声明一个委托
        public delegate void DisplayUpdateDelegate(string str);
        //声明事件
        public event DisplayUpdateDelegate ShowUpdate;
        private void Form2_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (ShowUpdate != null)
            {
                ShowUpdate(textBox1.Text.ToString());
            }
        }

父窗体 

   private void button3_Click(object sender, EventArgs e)
        {
            Form2 _frm2 = new Form2();
            _frm2.ShowUpdate += new Form2.DisplayUpdateDelegate(ShowMessage);
            _frm2.Show();
        }

        private void ShowMessage(string str)
        {
            textBox1.Text = str;
        }

 

2.父窗体的事件刷新子窗体的值

   父窗体代码

  

  public delegate void ChangeSonWindowDelegate(string str);
        ChangeSonWindowDelegate _changeSonWindow;
        private void button1_Click(object sender, EventArgs e)
        {

            Form2 _frm2 = new Form2();
             _changeSonWindow = new ChangeSonWindowDelegate(_frm2.ShowMessage);
            _frm2.Show();

        }
     
        private void button2_Click(object sender, EventArgs e)
        {

            _changeSonWindow(textBox1.Text);

        }

子窗体代码 

        public void ShowMessage(string str)
        {
            textBox1.Text = str;

        }