I have a Windows Forms Application, that starts a Thread when loading. The thread starts a ServiceHost which exposes a WCF service.
Here the code who start the Thread:
Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim th As New Thread(AddressOf (New Ecoute).Ecouter)
th.Start()
End Sub
Here the code who create the service Host
Sub Ecouter()
host = New ServiceHost(GetType(ServiceEmulateur3270))
host.AddServiceEndpoint(GetType(IEmulateur3270), New NetNamedPipeBinding(), "net.pipe://localhost")
host.Open()
End Sub
When I receive a WCF call, in the service's called method, I want to update a control in the main form of my application. How can I get a reference to this Form ?
I found this Winforms, get form instance by form name but this show how to create a new instance of the form, but I want to get the currently loaded form instead.
OrElse, is it possible for the Thread to pass a reference of the form to the WCF service class ?
You should use the ParameterizedThreadStart constructor and pass the Form instance for example, something like this:
Dim th As New Thread(AddressOf (New Ecoute).Ecouter)
th.Start(this)
Sub Ecouter(ByVal data As Object)
' you can safely cast data as a Form
End Sub
Related
I have inherited an a VB.NET WinForms application. It is very poorly written with a lot of bad practices. The first order of business is to get some DI into the app with a container to resolve the dependencies so I can start breaking this thing up and getting it under test.
This is my first WinForms app and I am learning the nuances of a non-request based application on a single thread.
I am using Simple Injector as the IoC container.
One of my use cases that I need to refactor is a UserControl that is extending a DevExpress XtraUserControl.
From the Simple Injector docs:
Note: It is not possible to use Constructor Injection in User Controls. User Controls are required to have a default constructor. Instead, pass on dependencies to your User Controls using Method Injection.
I am following the docs verbatim on how to set up property injection:
IPropertySelectionBehavior
Here is my configuration:
Private Shared Sub Bootstrap()
Container = New Container()
Container.Options.DefaultScopedLifestyle = New ThreadScopedLifestyle()
Container.Options.PropertySelectionBehavior = New ImportPropertySelectionBehavior()
Container.Register(Of ICommissionManager, CommissionManager)(Lifestyle.Singleton)
Container.Register(Of frmMain, frmMain)(Lifestyle.Singleton)
Container.Register(Of viewSalesCustomers, viewSalesCustomers)(Lifestyle.Transient)
'https://stackoverflow.com/questions/38417654/winforms-how-to-register-forms-with-ioc-container/38421425
Dim registration As Registration = Container.GetRegistration(GetType(viewSalesCustomers)).Registration
registration.SuppressDiagnosticWarning(DiagnosticType.DisposableTransientComponent, "a reason")
Container.Verify()
End Sub
The user control:
Public Class viewSalesCustomers
Inherits DevExpress.XtraEditors.XtraUserControl
<Import>
Public Property CommissionManager As ICommissionManager
...redacted...
Private Sub viewSalesCustomers_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim commissions As ICollection(Of Commission)
commissions = CommissionManager.Get(Function(commission) commission.CommissionId = 1) <-- Always nothing (null)
End Sub
I know the container is resolving for anything deriving from Form (I tested it through constructor injection).
Not sure what I missing here on the property injection for this control.
UPDATE:
#Steven was spot on. I found where they are instantiating the control.
Private Sub BarSubItem2_ItemClick(ByVal sender As Object, ByVal e As DevExpress.XtraBars.ItemClickEventArgs) Handles BarSubItem2.ItemClick
Cursor = Cursors.WaitCursor
'Dim mView as New viewSalesCustomers()
Dim mView As viewSalesCustomers
mView = Program.Container.GetInstance(Of viewSalesCustomers)
showViewer(mView, "viewSalesCustomers")
Cursor = Cursors.Default
End Sub
Branching off a previous question... Retrieving only PRINT command from SQL Server procedure in VB.NET
I was able to dump all the text from SQL Server's messages and use what I need but for some reason I am unable to update my textbox with the events.
Private Shared Sub OnInfoMessage(ByVal sender As Object, ByVal e As System.Data.SqlClient.SqlInfoMessageEventArgs)
Dim Counter As Integer
Counter = 1
For Each line In e.Message.Split(vbNewLine)
If (line.Contains("====")) Then
RestoreTool.txtTRNStatus.Text = "TRN #" & Counter & "Restored"
Using LogFile As IO.StreamWriter = New IO.StreamWriter("C:\SDBT\worklog.ft", True)
LogFile.WriteLine(line)
End Using
Counter += 1
End If
Next
Everything runs smoothly but the textbox (txtTRNStatus) does not update with anything and remains blank (Where it should be showing "TRN #1 Restored")
I am utilizing a Background Worker as well to call the procedure that actually performs the restoration of a database. That procedure is what contains the event handler for the SQLInfoMessages.
Dim SQL As SqlCommand
Dim DBConn As New SqlConnection(ConnectionString)
SQL = New SqlCommand(DBScript, DBConn)
AddHandler DBConn.InfoMessage, New SqlInfoMessageEventHandler(AddressOf OnInfoMessage)
Dim SQLResult As IAsyncResult = SQL.BeginExecuteNonQuery()
Try
Catch e As Exception
MessageBox.Show(e.Message)
End Try
SQL.EndExecuteNonQuery(SQLResult)
CompletedTask = True
DBConn.Close()
I have a feeling the only way I can get the text to update is through the addition of something in the DoWork() portion of the Backgroundworker but cannot figure out what exactly. Can the OnInfoMessages be called at will when an update is needed or is it only specific to where the Event Handler is?
As you can see in the image, It's during the actual "restoration" that the tool would normally report which transaction log has been restored based off of the SQL Message received but it remains blank...
Thank you once again!
EDIT: My progress update for my background worker is set up correctly, I just am having trouble calling events from the OnInfoMessage Sub as a progress update which is where gets the next line from SQL.
Make sure you use the backgroundworker properly. In the "doWork" there must not have any line of code that affect the UI(UserInterface) as this thread isn't the main thread of the application. If it does, it will either crash or do nothing.
So if you need to change the UI from the background worker you will need to tell the main thread to do so from the "DoWork" method. This can be achieved by hooking a callback to event "ProgressChanged" of your backgroundWorker object.
' This event handler updates the UI. '
Private Sub backgroundWorker1_ProgressChanged( _
ByVal sender As Object, ByVal e As ProgressChangedEventArgs) _
Handles backgroundWorker1.ProgressChanged
Me.txtTRNStatus.Text = e.UserState.ToString()//Update UI
End Sub
From the "DoWork" method, raise this event like shown below to tell main thread to update UI. Use the second parameter to pass whatever is needed by main thread to do so.
Private Sub backgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs)
' This method will run on a thread other than the UI thread. '
' Be sure not to manipulate any Windows Forms controls created'
' on the UI thread from this method.'
Dim SomeObject As [Object]
//some stuff
backgroundWorker.ReportProgress(1, SomeObject)
//some stuff
backgroundWorker.ReportProgress(2, SomeObject)
End Sub
See MSDN for more detail on backgroundworker usage.
Or you could just use "invoke" like #Mark suggested in the comment. This tell main thread execute a sub. As long as the UI update is done by the main thread you will be fine.
I have been working thru this WPF example and am trying to hook it up to my database using Entity Framework but am confused on how to do this. Can someone please offer some guidance on how this would be done?
The code has the following in CustomerRepository.cs
static List<Customer> LoadCustomers(string customerDataFile)
{
// In a real application, the data would come from an external source,
// but for this demo let's keep things simple and use a resource file.
using (Stream stream = GetResourceStream(customerDataFile))
using (XmlReader xmlRdr = new XmlTextReader(stream))
return
(from customerElem in XDocument.Load(xmlRdr).Element("customers").Elements("customer")
select Customer.CreateCustomer(
(double)customerElem.Attribute("totalSales"),
(string)customerElem.Attribute("firstName"),
(string)customerElem.Attribute("lastName"),
(bool)customerElem.Attribute("isCompany"),
(string)customerElem.Attribute("email")
)).ToList();
}
which is where I assume the hook to the database would happen but not sure how. I can create the Model.edmx file to connect to the database but not sure how to physically get the list of customers from the database.
Also, this example uses a List of Customers but most examples I have gone through use ObservableCollection for this type of data. Is one preferable over the other and why?
TIA,
Brian Enderle
My MVVM/EF projects typically load entities directly into the ViewModels or Into light collections in the view models. I don't create any kind of custom repository to sit between them.
Generally my ViewModels do one of two things,
Retrieves data on instancing
Takes an entity as a constructor argument.
When I retrieve data on instance, I generally use a background worker class, which queries the context, puts the results in a list, and passes the list out. The Work Completed method then puts the entities into viewmodels and puts the ViewModels in a ObservableCollection.
Similar to this:
Private WithEvents GetProjectsBackgroundWorker As BackgroundWorker
Private _Projects As New ObservableCollection(Of ProjectViewModel)
Public Sub New()
GetProjectsBackgroundWorker = New BackgroundWorker
GetProjectsBackgroundWorker.RunWorkerAsync()
End Sub
Public Property Projects() As ObservableCollection(Of ProjectViewModel)
Get
Return _Projects
End Get
Set(ByVal value As ObservableCollection(Of ProjectViewModel))
_Projects = value
End Set
End Property
#Region " GetProjects"
Private Sub GetProjectsBackgroundWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles GetProjectsBackgroundWorker.DoWork
Dim results = From proj As Project In Context.Projects Where proj.flgActive = True And proj.flgReview = True Select proj
Dim ProjList As New List(Of Project)(results)
e.Result = ProjList
End Sub
Private Sub GetProjectsBackgroundWorker_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles GetProjectsBackgroundWorker.RunWorkerCompleted
If e.Error Is Nothing Then
For Each p As Project In e.Result
Projects.Add(New ProjectViewModel(p, Context))
Next
Else
End If
End Sub
#End Region
In ViewModels that take an entity as an argument, they often take a context as argument, especially if something is a short time-span operation. Otherwise I detach entities from the context in the even something goes hay-wire with the database or the connection is lost or something.
To answer your second question, ObservableCollections are Enumerable collections that have collection change notification implemented. The collection will notify the UI when a new item is added/removed/moved. Typically any time I have entities that are going to be viewed or displayed in the UI, I host them in an Observable Collection. Otherwise I use something simpler, a List normally.
I'm using the below to restore a database in VB.NET.
This works but causes the interface to lockup if the user clicks anything.
Also, I cannot get the progress label to update incrementally, it's blank until the backup is complete then displays 100%
Sub DoRestore()
Dim svr As Server = New Server("Server\SQL2008")
Dim res As Restore = New Restore()
res.Devices.AddDevice("C:\MyDB.bak", DeviceType.File)
res.Database = "MyDB"
res.RelocateFiles.Add(New RelocateFile("MyDB_Data", "C:\MyDB.mdf"))
res.RelocateFiles.Add(New RelocateFile("MyDB_Log", "C:\MyDB.ldf"))
res.PercentCompleteNotification = 1
AddHandler res.PercentComplete, AddressOf ProgressEventHandler
res.SqlRestore(svr)
End Sub
Is this change correct?:
Private Sub ProgressEventHandler(ByVal sender As Object, ByVal e As PercentCompleteEventArgs)
UpdateProgressBar(e.Percent)
End Sub
Private Sub UpdateProgressBar(ByVal e As String)
ProgressBar.Value = e
Status.Text = e.ToString
End Sub
You need to use SqlRestoreAsync not SqlRestore to prevent it tying up your main thread.
Then to avoid the Cross Thread Operation error when updating the UI you can use the approach here. Where you create a method on the form that will update the UI elements and call that from your asynch handler using Invoke.
We have an issue in our Silverlight application which uses WCF and Entity Framework, where we need to trap the event whenever a user shuts down the application by closing the web page or the browser instead of closing the silverlight application. This is in order to verify if any changes have been made, in which case we would ask the user if he wants to save before leaving.
We were able to accomplish the part which consists in trapping the closing of the web page: we wrote some code in the application object that have the web page call a method in the silverlight application object. The problem starts when in this method, we do an asynchroneous call to the Web Service to verify if changes have occured (IsDirty). We are using a DispatcherTimer to check for the return of the asynchroneous call. The problem is that the asynchroneous call never completes (in debug mode, it never ends up stepping into the _BfrServ_Customer_IsDirtyCompleted method), while it used to work fine before we added this new functionality.
You will find belowthe code we are using.
I am new to writing timers in combination with asynchroneous call so I may be doing something wrong but I cannot figure out what. I tried other things also but we without any success..
====================== CODE ==============================================
''# Code in the application object
Public Sub New()
InitializeComponent()
RegisterOnBeforeUnload()
_DispatcherTimer.Interval = New TimeSpan(0, 0, 0, 0, 500)
End Sub
Public Sub RegisterOnBeforeUnload()
''# Register Silverlight object for availability in Javascript.
Const scriptableObjectName As String = "Bridge"
HtmlPage.RegisterScriptableObject(scriptableObjectName, Me)
''# Start listening to Javascript event.
Dim pluginName As String = HtmlPage.Plugin.Id
HtmlPage.Window.Eval(String.Format("window.onbeforeunload = function () {{ var slApp = document.getElementById('{0}'); var result = slApp.Content.{1}.OnBeforeUnload(); if(result.length > 0)return result;}}", pluginName, scriptableObjectName))
End Sub
Public Function OnBeforeUnload() As String
Dim userControls As List(Of UserControl) = New List(Of UserControl)
Dim test As Boolean = True
If CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0).GetType().Name = "MainPage" Then
If Not CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).FindName("Tab") Is Nothing Then
If CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).FindName("Tab").Items.Count >= 1 Then
For Each item As TabItem In CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).Tab.Items
If item.Content.GetType().Name = "CustomerDetailUI"
_Item = item
WaitHandle = New AutoResetEvent(False)
DoAsyncCall()
Exit
End If
Next
End If
End If
End If
If _IsDirty = True Then
Return "Do you want to save before leaving."
Else
Return String.Empty
End If
End Function
Private Sub DoAsyncCall()
_Item.Content.CheckForIsDirty(WaitHandle) ''# This code resides in the CustomerDetailUI UserControl - see below for the code
End Sub
Private Sub _DispatcherTimer_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles _DispatcherTimer.Tick
If Not _Item.Content._IsDirtyCompleted = True Then
Exit Sub
End If
_DispatcherTimerRunning = False
_DispatcherTimer.Stop()
ProcessAsyncCallResult()
End Sub
Private Sub ProcessAsyncCallResult()
_IsDirty = _Item.Content._IsDirty
End Sub
''# CustomerDetailUI code
Public Sub CheckForIsDirty(ByVal myAutoResetEvent As AutoResetEvent)
_AutoResetEvent = myAutoResetEvent
_BfrServ.Customer_IsDirtyAsync(_Customer) ''# This method initiates asynchroneous call to the web service - all the details are not shown here
_AutoResetEvent.WaitOne()
End Sub
Private Sub _BfrServ_Customer_IsDirtyCompleted(ByVal sender As Object, ByVal e As BFRService.Customer_IsDirtyCompletedEventArgs) Handles _BfrServ.Customer_IsDirtyCompleted
If _IsDirtyFromRefesh Then
_IsDirtyFromRefesh = False
If e.Result = True Then
Me.Confirm("This customer has been modified. Are you sure you want to refresh your data ? " & vbNewLine & " Your changes will be lost.", "Yes", "No", Message.CheckIsDirtyRefresh)
End If
Busy.IsBusy = False
Else
If e.Result = True Then
_IsDirty = True
Me.Confirm("This customer has been modified. Would you like to save?", "Yes", "No", Message.CheckIsDirty)
Else
Me.Tab.Items.Remove(Me.Tab.SelectedItem)
Busy.IsBusy = False
End If
End If
_IsDirtyCompleted = True
_AutoResetEvent.Set()
End Sub
Your problem is that the DispatchTimer is trying to execute code on the same thread that you are blocking with the Wait. Hence it can't deliver the tick.
I'm not sure I'm clear why you need the timer at all. Why not simply block the UI thread (as in fact you already doing) directly in the call to OnBeforeUnload. Then have the asynchronous callback function set the wait handle after it has assigned the value of _IsDirty.
Follow the Wait with your message boxes.