判断窗体类是否已经被实例化

[lunyx]

有个窗体类，CForm1,怎么判断他已经被实例化了？也就是是否已经存在该类的对象，如果有的话，就把他显示出来，不用再重复建立了。谢谢，不要通过窗体的名称来判断，要通过类CForm1 来判断。

[gsyst520]

public static CForm1 cform1;

if (cform1== null || cform1.IsDisposed)
{
    cform1= new CForm1();
}
cform1.MdiParent = this;
cform1.StartPosition = FormStartPosition.CenterScreen;
cform1.Show();
cform1.Activate();

[zgke]

建立全局静态变量保存 CForm1 的实例

public static CForm1 m_CForm1;



判断的时候 直接 if(xxx.m_CForm1!=null)就可以了.

[冷月孤峰]

#region 不重复打开MDI子窗体
        /// <summary>
        /// 不重复打开MDI子窗体
        /// 调用：this.OpenMDIWindow(typeof(窗体名).ToString());
        /// </summary>
        /// <param name="ChildTypeString">窗体名称(typeof(FormName).ToString())</param>
        private void OpenMDIWindow(string ChildTypeString)
        {
            Form myChild = null;
            if (!ContainMDIChild(ChildTypeString))
            {
                // Get current process assembly
                Assembly assembly = Assembly.GetExecutingAssembly();
                // Create data type using type string
                Type typForm = assembly.GetType(ChildTypeString);
                // Create object using type's "InvokeMember" method
                Object obj = typForm.InvokeMember(
                    null,
                    BindingFlags.DeclaredOnly |
                    BindingFlags.Public | BindingFlags.NonPublic |
                    BindingFlags.Instance | BindingFlags.CreateInstance,
                    null,
                    null,
                    null);
                // Show child form 
                if (obj != null)
                {
                    this.Refresh();
                    //Form frmTip = LoadTip.ShowTipForm(this, "正在加载窗体...");

                    myChild = obj as Form;
                    myChild.MdiParent = this;
                    myChild.WindowState = FormWindowState.Maximized;
                    myChild.Show();
                    myChild.Focus();

                    //frmTip.Close();

                }
            }
        }

        /// <summary>
        /// Search mdi child form by specific type string
        /// </summary>
        /// <param name="ChildTypeString"></param>
        /// <returns></returns>
        private bool ContainMDIChild(string ChildTypeString)
        {
            Form myMDIChild = null;
            foreach (Form f in this.MdiChildren)
            {
                if (f.GetType().ToString() == ChildTypeString)
                {
                    // found it 
                    myMDIChild = f;
                    break;
                }
            }
            // Show the exist form
            if (myMDIChild != null)
            {
                myMDIChild.TopMost = true;
                myMDIChild.Show();
                myMDIChild.Focus();
                return true;
            }
            else
            {
                return false;
            }
        }
        #endregion 

[xutao888]

用单例模式

[wartim]

一开始赋成null，new过了就不是null