如何获取申请表的parent？

Question

我在 "Cammon" class 中创建了一个方法。此方法的功能是检查设置变量，从那里打开正确的表单作为 MID child.

这是我的方法

   public static void OpenMyForm(string sectionName, string[] keys, Form myform) {
        //make sure there are no other forms of the ame type open
        foreach (Form form in Application.OpenForms) {
            if (form.GetType() == myform.GetType()) {
                form.Activate();
                return;
            }
        }

        if (Settings._AuthenticationMode == "Thumbprint") {

            var newMDIChild = myform;

            // Set the Parent Form of the Child window.
            newMDIChild.MdiParent = Main.ActiveForm;

            // Display the new form.
            newMDIChild.Show();
        }


        if (Settings._AuthenticationMode == "Single" && UserInfo.Autherized == true) {

            var role = new Roles();

            if (role.hasAccess(sectionName, keys)) {
                var newMDIChild = myform;

                // Set the Parent Form of the Child window.
                newMDIChild.MdiParent = Main.ActiveForm;

                // Display the new form.
                newMDIChild.Show();
            }
            else {
                Common.Alert("You do not have a permissions to perform this action!");
            }
        }
    }

这里的问题是当我调用此方法时出现异常错误。

但是，当我调用此方法时，新表单实际上会在我收到错误之前打开。

我认为问题出在下面这行

newMDIChild.MdiParent = Main.ActiveForm;

我认为我设置 parent 的方式不正确。 Main()

中的 parent 表单名称

这是我如何调用此方法的示例

Common.OpenMyForm("Vendors", new string[] { "add" }, new DepartmentsAdd());

我该如何解决这个问题？

System.NullReferenceException was unhandled
  HResult=-2147467261
  Message=Object reference not set to an instance of an object.
  Source=Telerik.WinControls.UI
  StackTrace:
       at Telerik.WinControls.UI.RadListElement.HandleMouse(Object sender, RoutedEventArgs args)
       at Telerik.WinControls.UI.RadListElement.OnBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.DoMouseUp(MouseEventArgs e)
       at Telerik.WinControls.ComponentInputBehavior.OnMouseUp(MouseEventArgs e)
       at Telerik.WinControls.RadControl.OnMouseUp(MouseEventArgs e)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at Telerik.WinControls.RadControl.WndProc(Message& m)
       at Telerik.WinControls.UI.RadPopupControlBase.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at RM.Program.Main()
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

Answer 1

实现派生自 ApplicationContext 的应用程序上下文 class：

class MyApplicationContext : ApplicationContext
{
  public static MyApplicationContext CurrentContext;

   public MyApplicationContext(Form mainForm) : base(mainForm)
   {
     //...implement any hooks, additional context etc.

     CurrentContext = this;
   }
}

使用您的应用程序上下文的实现：

[STAThread]
static void Main(string[] args) 
{

  var context = new MyApplicationContext(new MainForm());

   // Run the application with the specific context.
   Application.Run(context);

 }

要访问您的应用程序上下文数据，例如 MainForm：

MyApplicationContext.CurrentContext.MainForm

因此：

// Set the Parent Form of the Child window.
newMDIChild.MdiParent = MyApplicationContext.CurrentContext.MainForm;

如何获取申请表的parent？

How to get the parent form of an application?

c#

winforms

parent-child