本次目標是建立一個Form主窗體，並在該主窗體中建立菜單，通過菜單打開其余的子窗體。

Form1圖片：

代碼：

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

namespace WindowsFormsApp1
{
    
 
public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 

        private void menuItem3_Click(object sender, EventArgs e)
        {

            {
                //foreach (Form childrenForm in this.MdiChildren)
                //{
                
 
//    if (childrenForm.Name == "Form2")
                //    {
                //        childrenForm.Visible = true;
                //        childrenForm.Activate();
                //        return;
                //    }
                //}

               int i = OnlyOne("Form2");
                if (i == 0
 
)
                {
                    Form2 Mdichild = new Form2();
                    Mdichild.MdiParent = this;
                    Mdichild.Show();
                   // this.LayoutMdi(MdiLayout.TileHorizontal);
                }
                else
                    return;
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void menuItem4_Click(object sender, EventArgs e)
        {
            int a = OnlyOne("Form2");
            if (a == 0)
           
            {
                Form2 MdiChild1 = new Form2();
                MdiChild1.MdiParent = this;
                MdiChild1.Show();
                //this.LayoutMdi(MdiLayout.TileHorizontal);
            }
            else
                return;
        }

        private void menuItem5_Click(object sender, EventArgs e)
        {
            int b = OnlyOne("Form4");
            if (b == 0)
            {
                Form4 MdiChild2 = new Form4();
                MdiChild2.MdiParent = this;
                MdiChild2.Show();
                //this.LayoutMdi(MdiLayout.TileHorizontal);
            }
            else
                return;

        }

      public int OnlyOne(string xx)     //不重復打開mdi窗口整合成一個方法
        {
            
            foreach (Form childrenForm in this.MdiChildren)
            {
                if (childrenForm.Name == xx)
                {
                    childrenForm.Visible = true;
                    childrenForm.Activate();//有這個，from必須要有可焦點的，如textbox，去掉則不用
                    return 1;
                }
            }
            return 0;
        }
    }
}

Form2圖片：

代碼：

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

namespace WindowsFormsApp1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            comboBox1.SelectedIndex = 0;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "")
                MessageBox.Show("禁止為空", "信息提示");
            else
            {
               // this.Hide();
                Form3 childForm3 = new Form3(this.textBox1.Text,this.comboBox1.SelectedItem.ToString(),this.listBox1.Text);
                childForm3.MdiParent = this.MdiParent;
                childForm3.Show();  

            }
        }
    }
}

Form3圖片：

代碼：

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

namespace WindowsFormsApp1
{
    public partial class Form3 : Form
    {
        private string _varname;
        private string _varSubject;
        private string _varFeedBack;
        public Form3(string varName, string varSubject, string varFeedBack)
        {
            InitializeComponent();
            this._varname = varName;
            this._varSubject = varSubject;
            this._varFeedBack = varFeedBack;
            listBox1.Items.Add("姓名:" + _varname);
            listBox1.Items.Add("主題:" + _varSubject);
            listBox1.Items.Add("意見:" + _varFeedBack);

        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}

Form4圖片：

代碼：

無特殊功能代碼。

窗口1的單擊事件，得到Form2:

   Form2 Mdichild = new Form2();
   Mdichild.MdiParent = this;    //制定即將打開的Form2對象MdiParent,即Form2對象的MDI父窗口為當前主窗口
   Mdichild.Show();

MDI窗體的排列：

(1)層疊

this.LayoutMdi(MdiLayout.Cascade);

(2)水平平鋪

this.LayoutMdi(MdiLayout.TileHorizontal);

(3)垂直平鋪

this.LayoutMdi(MdiLayout.TileVertical);

窗體傳值，接受來自Form2的數據信息。

    private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "")
                MessageBox.Show("禁止為空", "信息提示");
            else
            {
               // this.Hide();
                Form3 childForm3 = new Form3(this.textBox1.Text,this.comboBox1.SelectedItem.ToString(),this.listBox1.Text);
                childForm3.MdiParent = this.MdiParent;
                childForm3.Show();  

            }
        }

確保子窗體在轉換的過程中受到MDI主窗口的控制

 childForm3.MdiParent = this.MdiParent;

防止重復打開窗口

        private void menuItem3_Click(object sender, EventArgs e)
        {
                 foreach (Form childrenForm in this.MdiChildren)
                {
                    if (childrenForm.Name == "Form2")
                    {
                        childrenForm.Visible = true;
                        childrenForm.Activate();
                        return;
                    }
                }
               Form2 Mdichild = new Form2();
               Mdichild.MdiParent = this;
               Mdichild.Show();

         }
    

由於每個打開的窗體都可能會用到上面的代碼，因此建議將之集成方法後統一調用。

但是要註意return在防止打開窗口中起到的作用，應用到方法中的函數後，return跳不出事件函數，所以采取了如下方法：

 public int OnlyOne(string xx)     //不重復打開mdi窗口整合成一個方法
        {
            
            foreach (Form childrenForm in this.MdiChildren)
            {
                if (childrenForm.Name == xx)
                {
                    childrenForm.Visible = true;
                    childrenForm.Activate();//有這個，from必須要有可焦點的，如textbox，去掉則不用
                    return 1;
                }
            }
            return 0;
        }

如若沒有文本框激活焦點，則不用寫childrenFrom.Activate();

2017-12-04 16:56:54

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