Bind a List to a DataGridView which is filled by an other thread

In .NET v1.1 I already tried to implement a List that tells the DataGrid that it was updated. I managed this through deriving a class from System.Collections.CollectionBase and overriding a bunch of Methods. The Problem was whenever I chaned a property of an item which was already added to this list nothing was updated. I had to implement Events and update the List on my own. Everything was connected and everytime I wanted to use the list for an other Item Type I had to write a lot lines of code. What a waste of time.

Then a few days ago I took a look at Visual Studio 2005 Beta2 and discovered a Class named BindingList which will inform the databinding Control that itself is updated. Besides it is a generic list which makes that thing more type-safe.
I bound the list to a DataGridView and added some items. To cause an update when a bound item's property is changed I had to implement System.ComponentModel.INotifyPropertyChanged Interface. This Interface delivers the PropertyChanged event which informs the databinding control that itself was changed. I think this is a dirty solution but better than .NET v1 in any way.
I implemented the Interface on all objects and raised the event delivered whenever I changed a property. Great job! Everything worked fine!

I didn't care about that thing anymore because it worked fine and integrated it into my application. But I didn't think that multi-threading is such a heavy problem for this Microsoft guys because everytime an item was changed by an other thread I got an exception. Fortunatelly I already implemented a Service which provides UiSafety so I simply had to call this service before I rose the event and my list were updated correctly.

I think noone will talk about in any TechTalk or PDC but in my oppinion it is a great feature saving a lot lines of code although you have to care for thread safety on your own. Good job Microsoft!

Comments

Post a Comment

Popular posts from this blog

Custom Chrome in WPF

Image
Some of you may have wondered who the creators of Microsoft Max did the Chrome. Although this breaks one of the Top 10 Vista rules I will show how to create a WPF window with custom chrome. You can't get there by simply setting the border of a WPF Window to None because always a thick border remains. You have to do a work around and create an empty Win32 window and fill it with your own WPF controls. You can use the HwndSource object to do this. This object is intended to place WPF controls into Win32 Applications but you can also use it to place a WPF control onto your Windows Desktop which is also a Win32 application. HwndSource will call the native function CreateWindowEx and create the window for you. Dim params As HwndSourceParameters = New HwndSourceParameters("CustomChrome 1", 400, 300) Dim hwnd As HwndSource = New HwndSource(params) hwnd.RootVisual = New Page1 This code will create a default window for you. The HwndSourceParameters 's constructor sets the
Read more

Capture WebCam with WinForms2

I was asked whether it is possible to capture a webcam's output in Windows Forms 2.0 so I did a bit researching. First I thought I would have to do this in DirectX but then I found some API calls for VB6 and translated them to VB .NET 2. In fact it is very easy to capture the output. You simply need a Control and it's handle. I chose a PictureBox named PictureBox1 to do so. You have to define the Win32 API calls first. We will need two API functions SendMessage and capCreateCaptureWindow . Private Declare Auto Function SendMessage Lib "user32" (ByVal hwnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer Const EM_LINEFROMCHAR As Integer = &HC9 Const EM_LINEINDEX As Integer = &HBB Private Declare Auto Function capCreateCaptureWindow Lib "avicap32.dll" (ByVal lpszWindowName As String, ByVal dwStyle As Integer, ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Inte
Read more

WPF: Binding updates

Whenever you offer a Cancel Changes command you need to delay updates to the Source until the user Accepts Changes e.g. by clicking OK or Save. Although WPF's two way bindings update the source immediately you can delay the update by adding UpdateSourceTrigger=Explicit to your binding expression. {Binding Path=Text, UpdateSourceTrigger=Explicit} The Source won't be updated until you call BindingExpression.UpdateSource .
Read more