随着Winform项目越来越多，界面上显示的窗体越来越多，窗体管理变得更加繁琐。有时候我们要打开新窗体，然后关闭多余的其他窗体，这个时候如果一个一个去关闭就会变得很麻烦，而且可能还会出现遗漏的情况。这篇文章介绍了三种方式实现"Winform父窗体打开新的子窗体前，关闭其他子窗体"的方案。

代码：

   public partial class MainForm : Form
   {
       private UserControl userControl;
       private UserControl1 userControl1;
       private UserControl2 userControl2;

       private Form1 form1;
       private Form2 form2;
       public MainForm()
       {
           InitializeComponent();
           this.IsMdiContainer = true;
           userControl1 = new UserControl1();
           userControl2 = new UserControl2();

           form1 = new Form1();
           form2 = new Form2();
       }



       private void btnForm1_Click(object sender, EventArgs e)
       {
           方法一
           //ShowEmbeddedForm(1);

           方法二
           //form1.MdiParent = this;
           //OpenMdiForm(form1);

           //方法三
           OpenNewChildForm(form1);
       }

       private void btnForm2_Click(object sender, EventArgs e)
       {
           方法一
           //ShowEmbeddedForm(2);

           方法二
           //form2.MdiParent = this;
           //OpenMdiForm(form2);

           //方法三
           OpenNewChildForm(form2);

       }

       /// <summary>
       /// 关闭所有子窗体
       /// </summary>
       /// <param name="sender"></param>
       /// <param name="e"></param>
       private void btnHidden_Click(object sender, EventArgs e)
       {
           panelForm.Controls.Clear();

           // 关闭所有子窗体
           for (int i = Application.OpenForms.Count - 1; i >= 0; i--)
           {
               var openForm = Application.OpenForms[i];
               if(openForm!=this)
               {
                   openForm.Close();
               }
           }
       }

       /// <summary>
       /// 方法一：使用内嵌方式将控件放入到Panel中，放入前清空Panel中的控件
       /// </summary>
       private void ShowEmbeddedForm(int type)
       {
           panelForm.Controls.Clear();
           if (type == 1)
           {
               panelForm.Controls.Add(userControl1);
           }
           else if (type == 2)
           {
               panelForm.Controls.Add(userControl2);
           }
       }

       /// <summary>
       /// 方法二：使用MDI实现父窗体每次只能显示一个子窗体
       /// 特点：子窗体内嵌到父窗体中
       /// </summary>
       /// <param name="子窗体名称"></param>
       private void OpenMdiForm(Form frm)
       {
           //判断是否第一次显示窗体
           if (this.MdiChildren.Length == 1)
           {
               frm.MdiParent = this;
               frm.Show();
               return;
           }
           foreach (Form children in this.MdiChildren)
           {
               if (frm == children)
               {
                   //如果是现在就存在的子窗体就激活它
                   children.Activate();
               }
               else
               {
                   children.Close();
                   if (frm == null || frm.IsDisposed)
                   {
                       Type type = frm.GetType();
                       frm = (Form)System.Activator.CreateInstance(type);
                       frm.MdiParent = this;
                       frm.Show();
                   }
                   else
                   {
                       frm.MdiParent = this;
                       frm.Show();
                   }
               }
           }
       }


       /// <summary>
       /// 方法三：使用OpenForms，在打开新窗体前关闭所有打开的子窗体
       /// </summary>
       /// <param name="newChildForm"></param>
       private void OpenNewChildForm(Form newChildForm)
       {
           // 关闭所有其他的子窗体
           for (int i = Application.OpenForms.Count-1; i >=0; i--) 
           {
               var openForm = Application.OpenForms[i];
               if (openForm != this && openForm != newChildForm)
               {
                   openForm.Close();
               }
           }
           // 打开新的子窗体
           if (newChildForm == null || newChildForm.IsDisposed)
           {
               Type type = newChildForm.GetType();
               newChildForm = (Form)System.Activator.CreateInstance(type);
               newChildForm.Show();
           }
           else
           {
               newChildForm.Show();
           }
       }
   }

实例链接：https://download.csdn.net/download/lvxingzhe3/89249982