Specifically this is a follow-up to this question DataGrid filter performance, but there are many more similar questions relating to WPF DataGrid performance on StackOverflow.
After a lot of profiling and going through .NET source code, I have realized that many performance issues, such as filtering and sorting, boil down just one issue: A CollectionView.Reset event does not recycle containers (like scrolling does).
What I mean is that instead of assigning the existing rows a new datacontext, all rows are removed from the visual tree, new rows are generated and added, and a layout cycle (measure and arrange) is performanced.
So the main question is: Has anyone successfully managed to work around this? E.g. by manually manipulating the ItemContainerGenerator, or by creating their own version of the DataGridRowsPresenter?
So this is the gist of my approach so far.
public class CollectionViewEx
{
public event EventHandler Refresh;
public override void Refresh()
{
Refresh?.Invoke(this, EventArgs.Empty);
}
}
public class DataGridEx : DataGrid
{
protected override OnItemsSourceChanged(IEnumerable oldSource, IEnumerable newSource)
{
if (newSource is CollectionViewEx cvx)
{
cvx.Refresh += (o,a) => OnViewRefreshing;
}
}
private void OnViewRefreshing()
{
RowsPresenter.Refresh();
}
}
public class DataGridRowsPresenterEx : DataGridRowsPresenter
{
public void Refresh()
{
var generator = (IRecyclingItemContainerGenerator)ItemContainerGenerator;
generator.Recycle(new GeneratorPosition(0, 0), ???);
RemoveInternalChildRange(0, VisualChildrenCount);
using (generator.StartAt(new GeneratorPosition(-1, 0), GeneratorDirection.Forward))
{
UIElement child;
bool isNewlyRealised = false;
while ((child = generator.GenerateNext(out isNewlyRealised) as UIElement) != null)
{
AddInternalChild(child);
generator.PrepareItemContainer(child);
}
}
}
}
But the results are very confusing - obviously because I don't quite understand how to work with the ICG.
I have looked through .net source code to see their implementations (when adding/removing/replacing items), and also found a couple of online resources on how to create a new virtualized panel (e.g. virtualizingwrappanel), but none really address this particular issue, where we want to reuse all existing containers for a new set of items.
So the secondary question is: Can anyone explain if this approach is even possible? How would I do it?
I never use reset directly from CollectionView because a methode on CollectionView's Source do it. This IList is modified for my needs. I did it like Paul McClean explained here.
In this class you could notify OnCollectionChanged to inform the CollectionView. sondergard explained what NotifyCollectionChangedAction.Reset do. But NotifyCollectionChangedAction.Replace keep running the recyling for the Items.
Maybe my research helps.
I'm using a simple ComboBox in GXT that gets its values from the database.
What I want is that everytime that the user clicks (expands) the ComboBox, it will check and re-populate it with the latest entries in the database (in case they've changed).
Right now I'm doing something like:
ProtocolProperties protocolProperties = GWT.create(ProtocolProperties.class);
final ListStore<ProtocolDto> protocolStore = new ListStore<ProtocolDto>(protocolProperties.id());
protocol = new ComboBox<ProtocolDto>(protocolStore, protocolProperties.name());
protocol.addExpandHandler(new ExpandHandler() {
#Override
public void onExpand(ExpandEvent event) {
protocolStore.clear();
ProtocolDto emptyDto = new ProtocolDto();
emptyDto.setId(-1);
emptyDto.setName("None");
protocolStore.add(emptyDto);
AppEntryPoint.getLogbookdataservice().getAllProtocols(new AsyncCallback<List<ProtocolDto>>() {
#Override
public void onSuccess(List<ProtocolDto> result) {
protocolStore.addAll(result);
}
#Override
public void onFailure(Throwable caught) {
// TODO Auto-generated method stub
}
});
}
});
Thanks to anyone who takes the time to answer this.
You should be looking at Async Support in Combobox instead of reinventing a square wheel.
Sencha Demo - http://www.sencha.com/examples/#ExamplePlace:advancedcombobox
Stackoverflow - Also one approach discussed here - Dynamic Autosuggest Combobox in GXT
GXT Forum - http://www.sencha.com/forum/showthread.php?185967-ComboBox-doQuery-method-seems-not-working-with-Remote-Loader
I want the user to select a directory where a file that I will then generate will be saved. I know that in WPF I should use the OpenFileDialog from Win32, but unfortunately the dialog requires file(s) to be selected - it stays open if I simply click OK without choosing one. I could "hack up" the functionality by letting the user pick a file and then strip the path to figure out which directory it belongs to but that's unintuitive at best. Has anyone seen this done before?
You can use the built-in FolderBrowserDialog class for this. Don't mind that it's in the System.Windows.Forms namespace.
using (var dialog = new System.Windows.Forms.FolderBrowserDialog())
{
System.Windows.Forms.DialogResult result = dialog.ShowDialog();
}
If you want the window to be modal over some WPF window, see the question How to use a FolderBrowserDialog from a WPF application.
EDIT: If you want something a bit more fancy than the plain, ugly Windows Forms FolderBrowserDialog, there are some alternatives that allow you to use the Vista dialog instead:
Third-party libraries, such as Ookii dialogs (.NET 4.5+)
The Windows API Code Pack-Shell:
using Microsoft.WindowsAPICodePack.Dialogs;
...
var dialog = new CommonOpenFileDialog();
dialog.IsFolderPicker = true;
CommonFileDialogResult result = dialog.ShowDialog();
Note that this dialog is not available on operating systems older than Windows Vista, so be sure to check CommonFileDialog.IsPlatformSupported first.
I created a UserControl which is used like this:
<UtilitiesWPF:FolderEntry Text="{Binding Path=LogFolder}" Description="Folder for log files"/>
The xaml source looks like this:
<UserControl x:Class="Utilities.WPF.FolderEntry"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<DockPanel>
<Button Margin="0" Padding="0" DockPanel.Dock="Right" Width="Auto" Click="BrowseFolder">...</Button>
<TextBox Height="Auto" HorizontalAlignment="Stretch" DockPanel.Dock="Right"
Text="{Binding Text, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}" />
</DockPanel>
</UserControl>
and the code-behind
public partial class FolderEntry {
public static DependencyProperty TextProperty = DependencyProperty.Register("Text", typeof(string), typeof(FolderEntry), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
public static DependencyProperty DescriptionProperty = DependencyProperty.Register("Description", typeof(string), typeof(FolderEntry), new PropertyMetadata(null));
public string Text { get { return GetValue(TextProperty) as string; } set { SetValue(TextProperty, value); }}
public string Description { get { return GetValue(DescriptionProperty) as string; } set { SetValue(DescriptionProperty, value); } }
public FolderEntry() { InitializeComponent(); }
private void BrowseFolder(object sender, RoutedEventArgs e) {
using (FolderBrowserDialog dlg = new FolderBrowserDialog()) {
dlg.Description = Description;
dlg.SelectedPath = Text;
dlg.ShowNewFolderButton = true;
DialogResult result = dlg.ShowDialog();
if (result == System.Windows.Forms.DialogResult.OK) {
Text = dlg.SelectedPath;
BindingExpression be = GetBindingExpression(TextProperty);
if (be != null)
be.UpdateSource();
}
}
}
}
As stated in earlier answers, FolderBrowserDialog is the class to use for this. Some people have (justifiable) concerns with the appearance and behaviour of this dialog. The good news is that it was "modernized" in NET Core 3.0, so is now a viable option for those writing either Windows Forms or WPF apps targeting that version or later (you're out of luck if still using NET Framework though).
In .NET Core 3.0, Windows Forms users [sic] a newer COM-based control that was introduced in Windows Vista:
To reference System.Windows.Forms in a NET Core WPF app, it is necessary to edit the project file and add the following line:
<UseWindowsForms>true</UseWindowsForms>
This can be placed directly after the existing <UseWPF> element.
Then it's just a case of using the dialog:
using System;
using System.Windows.Forms;
...
using var dialog = new FolderBrowserDialog
{
Description = "Time to select a folder",
UseDescriptionForTitle = true,
SelectedPath = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
+ Path.DirectorySeparatorChar,
ShowNewFolderButton = true
};
if (dialog.ShowDialog() == DialogResult.OK)
{
...
}
FolderBrowserDialog has a RootFolder property that supposedly "sets the root folder where the browsing starts from" but whatever I set this to it didn't make any difference; SelectedPath seemed to be the better property to use for this purpose, however the trailing backslash is required.
Also, the ShowNewFolderButton property seems to be ignored as well, the button is always shown regardless.
Ookii folder dialog can be found at Nuget.
PM> Install-Package Ookii.Dialogs.Wpf
And, example code is as below.
var dialog = new Ookii.Dialogs.Wpf.VistaFolderBrowserDialog();
if (dialog.ShowDialog(this).GetValueOrDefault())
{
textBoxFolderPath.Text = dialog.SelectedPath;
}
More information on how to use it: https://github.com/augustoproiete/ookii-dialogs-wpf
For those who don't want to create a custom dialog but still prefer a 100% WPF way and don't want to use separate DDLs, additional dependencies or outdated APIs, I came up with a very simple hack using the Save As dialog.
No using directive needed, you may simply copy-paste the code below !
It should still be very user-friendly and most people will never notice.
The idea comes from the fact that we can change the title of that dialog, hide files, and work around the resulting filename quite easily.
It is a big hack for sure, but maybe it will do the job just fine for your usage...
In this example I have a textbox object to contain the resulting path, but you may remove the related lines and use a return value if you wish...
// Create a "Save As" dialog for selecting a directory (HACK)
var dialog = new Microsoft.Win32.SaveFileDialog();
dialog.InitialDirectory = textbox.Text; // Use current value for initial dir
dialog.Title = "Select a Directory"; // instead of default "Save As"
dialog.Filter = "Directory|*.this.directory"; // Prevents displaying files
dialog.FileName = "select"; // Filename will then be "select.this.directory"
if (dialog.ShowDialog() == true) {
string path = dialog.FileName;
// Remove fake filename from resulting path
path = path.Replace("\\select.this.directory", "");
path = path.Replace(".this.directory", "");
// If user has changed the filename, create the new directory
if (!System.IO.Directory.Exists(path)) {
System.IO.Directory.CreateDirectory(path);
}
// Our final value is in path
textbox.Text = path;
}
The only issues with this hack are :
Acknowledge button still says "Save" instead of something like "Select directory", but in a case like mines I "Save" the directory selection so it still works...
Input field still says "File name" instead of "Directory name", but we can say that a directory is a type of file...
There is still a "Save as type" dropdown, but its value says "Directory (*.this.directory)", and the user cannot change it for something else, works for me...
Most people won't notice these, although I would definitely prefer using an official WPF way if microsoft would get their heads out of their asses, but until they do, that's my temporary fix.
Ookii Dialogs includes a dialog for selecting a folder (instead of a file):
https://github.com/ookii-dialogs
For Directory Dialog to get the Directory Path, First Add reference System.Windows.Forms, and then Resolve, and then put this code in a button click.
var dialog = new FolderBrowserDialog();
dialog.ShowDialog();
folderpathTB.Text = dialog.SelectedPath;
(folderpathTB is name of TextBox where I wana put the folder path, OR u can assign it to a string variable too i.e.)
string folder = dialog.SelectedPath;
And if you wana get FileName/path, Simply do this on Button Click
FileDialog fileDialog = new OpenFileDialog();
fileDialog.ShowDialog();
folderpathTB.Text = fileDialog.FileName;
(folderpathTB is name of TextBox where I wana put the file path, OR u can assign it to a string variable too)
Note: For Folder Dialog, the System.Windows.Forms.dll must be added to the project, otherwise it wouldn't work.
I found the below code on below link... and it worked
Select folder dialog WPF
using Microsoft.WindowsAPICodePack.Dialogs;
var dlg = new CommonOpenFileDialog();
dlg.Title = "My Title";
dlg.IsFolderPicker = true;
dlg.InitialDirectory = currentDirectory;
dlg.AddToMostRecentlyUsedList = false;
dlg.AllowNonFileSystemItems = false;
dlg.DefaultDirectory = currentDirectory;
dlg.EnsureFileExists = true;
dlg.EnsurePathExists = true;
dlg.EnsureReadOnly = false;
dlg.EnsureValidNames = true;
dlg.Multiselect = false;
dlg.ShowPlacesList = true;
if (dlg.ShowDialog() == CommonFileDialogResult.Ok)
{
var folder = dlg.FileName;
// Do something with selected folder string
}
I'd suggest, to add in the nugget package:
Install-Package OpenDialog
Then the way to used it is:
Gat.Controls.OpenDialogView openDialog = new Gat.Controls.OpenDialogView();
Gat.Controls.OpenDialogViewModel vm = (Gat.Controls.OpenDialogViewModel)openDialog.DataContext;
vm.IsDirectoryChooser = true;
vm.Show();
WPFLabel.Text = vm.SelectedFilePath.ToString();
Here's the documentation:
http://opendialog.codeplex.com/documentation
Works for Files, files with filter, folders, etc
The best way to achieve what you want is to create your own wpf based control , or use a one that was made by other people
why ? because there will be a noticeable performance impact when using the winforms dialog in a wpf application (for some reason)
i recommend this project
https://opendialog.codeplex.com/
or Nuget :
PM> Install-Package OpenDialog
it's very MVVM friendly and it isn't wraping the winforms dialog
The Ookii VistaFolderBrowserDialog is the one you want.
If you only want the Folder Browser from Ooki Dialogs and nothing else then download the Source, cherry-pick the files you need for the Folder browser (hint: 7 files) and it builds fine in .NET 4.5.2. I had to add a reference to System.Drawing. Compare the references in the original project to yours.
How do you figure out which files? Open your app and Ookii in different Visual Studio instances. Add VistaFolderBrowserDialog.cs to your app and keep adding files until the build errors go away. You find the dependencies in the Ookii project - Control-Click the one you want to follow back to its source (pun intended).
Here are the files you need if you're too lazy to do that ...
NativeMethods.cs
SafeHandles.cs
VistaFolderBrowserDialog.cs
\ Interop
COMGuids.cs
ErrorHelper.cs
ShellComInterfaces.cs
ShellWrapperDefinitions.cs
Edit line 197 in VistaFolderBrowserDialog.cs unless you want to include their Resources.Resx
throw new InvalidOperationException(Properties.Resources.FolderBrowserDialogNoRootFolder);
throw new InvalidOperationException("Unable to retrieve the root folder.");
Add their copyright notice to your app as per their license.txt
The code in \Ookii.Dialogs.Wpf.Sample\MainWindow.xaml.cs line 160-169 is an example you can use but you will need to remove this, from MessageBox.Show(this, for WPF.
Works on My Machine [TM]
None of these answers worked for me (generally there was a missing reference or something along those lines)
But this quite simply did:
Using FolderBrowserDialog in WPF application
Add a reference to System.Windows.Forms and use this code:
var dialog = new System.Windows.Forms.FolderBrowserDialog();
System.Windows.Forms.DialogResult result = dialog.ShowDialog();
No need to track down missing packages. Or add enormous classes
This gives me a modern folder selector that also allows you to create a new folder
I'm yet to see the impact when deployed to other machines
I know this is an old question, but a simple way to do this is use the FileDialog option provided by WPF and using System.IO.Path.GetDirectory(filename).
You could use smth like this in WPF. I've created example method.
Check below.
public string getFolderPath()
{
// Create OpenFileDialog
Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
OpenFileDialog openFileDialog = new OpenFileDialog();
openFileDialog.Multiselect = false;
openFileDialog.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
if (openFileDialog.ShowDialog() == true)
{
System.IO.FileInfo fInfo = new System.IO.FileInfo(openFileDialog.FileName);
return fInfo.DirectoryName;
}
return null;
}
It seems that the Microsoft.Win32 .NET library does not support selecting folders (only files), so you are out of luck in WPF (as of 7/2022). I feel the best option now is Ookii for WPF: https://github.com/ookii-dialogs/ookii-dialogs-wpf. It works great and as expected in WPF minus Microsoft support. You can get it as a NuGet package. Code behind XAML View:
public partial class ExportRegionView : UserControl
{
public ExportRegionView()
{
InitializeComponent();
}
private void SavePath(object sender, RoutedEventArgs e)
{
var dialog = new Ookii.Dialogs.Wpf.VistaFolderBrowserDialog();
dialog.Description = "SIPAS Export Folder";
dialog.UseDescriptionForTitle = true;
if (dialog.ShowDialog().GetValueOrDefault())
{
ExportPath.Text = dialog.SelectedPath;
}
}
}
XAML: <Button Grid.Row="1" Grid.Column="3" Style="{DynamicResource Esri_Button}" Click="SavePath" Margin="5,5,5,5">Path</Button>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace Gearplay
{
/// <summary>
/// Логика взаимодействия для OpenFolderBrows.xaml
/// </summary>
public partial class OpenFolderBrows : Page
{
internal string SelectedFolderPath { get; set; }
public OpenFolderBrows()
{
InitializeComponent();
Selectedpath();
InputLogicalPathCollection();
}
internal void Selectedpath()
{
Browser.Navigate(#"C:\");
Browser.Navigated += Browser_Navigated;
}
private void Browser_Navigated(object sender, NavigationEventArgs e)
{
SelectedFolderPath = e.Uri.AbsolutePath.ToString();
//MessageBox.Show(SelectedFolderPath);
}
private void MenuItem_Click(object sender, RoutedEventArgs e)
{
}
string [] testing { get; set; }
private void InputLogicalPathCollection()
{ // add Menu items for Cotrol
string[] DirectoryCollection_Path = Environment.GetLogicalDrives(); // Get Local Drives
testing = new string[DirectoryCollection_Path.Length];
//MessageBox.Show(DirectoryCollection_Path[0].ToString());
MenuItem[] menuItems = new MenuItem[DirectoryCollection_Path.Length]; // Create Empty Collection
for(int i=0;i<menuItems.Length;i++)
{
// Create collection depend how much logical drives
menuItems[i] = new MenuItem();
menuItems[i].Header = DirectoryCollection_Path[i];
menuItems[i].Name = DirectoryCollection_Path[i].Substring(0,DirectoryCollection_Path.Length-1);
DirectoryCollection.Items.Add(menuItems[i]);
menuItems[i].Click += OpenFolderBrows_Click;
testing[i]= DirectoryCollection_Path[i].Substring(0, DirectoryCollection_Path.Length - 1);
}
}
private void OpenFolderBrows_Click(object sender, RoutedEventArgs e)
{
foreach (string str in testing)
{
if (e.OriginalSource.ToString().Contains("Header:"+str)) // Navigate to Local drive
{
Browser.Navigate(str + #":\");
}
}
}
private void Goback_Click(object sender, RoutedEventArgs e)
{// Go Back
try
{
Browser.GoBack();
}catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void Goforward_Click(object sender, RoutedEventArgs e)
{ //Go Forward
try
{
Browser.GoForward();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void FolderForSave_Click(object sender, RoutedEventArgs e)
{
// Separate Click For Go Back same As Close App With send string var to Main Window ( Main class etc.)
this.NavigationService.GoBack();
}
}
}
I'm trying to write a ParentAdapter implementation; I'm interested in providing design-time support for some WPF controls I'm writing and this is how you manage custom logic for reparenting items to different container controls. I started small, with the notion of creating a StackPanel-derived class that would only allow Button elements to be parented at design-time (yes, I'm aware the panel itself needs code to support this as well.) I started with what I figured would be the simplest the ParentAdapter could be:
using System;
using System.Windows;
using System.Windows.Controls;
using Microsoft.Windows.Design.Interaction;
using Microsoft.Windows.Design.Model;
namespace ControlLibrary.Design
{
internal class SimplePanelParentAdapter : ParentAdapter
{
public override bool CanParent(ModelItem parent, Type childType)
{
return (childType == typeof(Button));
}
// moves the child item into the target panel; in this case a SimplePanel
public override void Parent(ModelItem newParent, ModelItem child)
{
using (ModelEditingScope undoContext = newParent.BeginEdit())
{
// is this correct?
//child.Content.SetValue("I'm in a custom panel!");
SimplePanel pnl = newParent.GetCurrentValue() as SimplePanel;
pnl.Children.Add(child.GetCurrentValue() as UIElement);
undoContext.Complete();
}
}
public override void RemoveParent(ModelItem currentParent, ModelItem newParent, ModelItem child)
{
// No special things need to be done, right?
child.Content.SetValue("I was in a custom panel.");
}
}
}
When I work with this at design-time, as soon as I drag a button over my custom panel, a NullReferenceException is thrown from deep within the VS code. My code is not throwing the exception, because I can step all the way through my method; the call stack indicates that code in Microsoft.Windows.Design.Developer.dll is throwing the exception.
Obviously I'm doing something incorrectly, but the documentation provides no examples and my search-fu seems to indicate that either no one is trying this or anyone who is trying it isn't talking about it. Does anyone have suggestions?
I found the answer to my question myself. The problem is caused by editing the model instead of the ModelItem wrapper. What I should have done (and does work) is something like this:
using System;
using System.Windows.Controls;
using Microsoft.Windows.Design.Interaction;
using Microsoft.Windows.Design.Model;
namespace ControlLibrary.Design
{
internal class SimplePanelParentAdapter : ParentAdapter
{
public override bool CanParent(ModelItem parent, Type childType)
{
return (childType == typeof(Button));
}
// moves the child item into the target panel; in this case a SimplePanel
public override void Parent(ModelItem newParent, ModelItem child)
{
using (ModelEditingScope undoContext = newParent.BeginEdit())
{
ModelProperty prop = newParent.Properties["Children"];
ModelItemCollection items = (ModelItemCollection)prop.Value;
items.Add(child);
undoContext.Complete();
}
}
public override void RemoveParent(ModelItem currentParent, ModelItem newParent, ModelItem child)
{
using (ModelEditingScope scope = child.BeginEdit())
{
ModelProperty prop = currentParent.Properties["Children"];
((ModelItemCollection)prop.Value).Remove(child);
scope.Complete();
}
}
}
}
I was confused when I wrote the first code and unsure how I was supposed to call Add() on the Children property; it looks like ModelProperty.Value wraps collections with ModelItemCollection, so unless you go out of your way to make your class use an obtuse interface this should work.
I am trying to unit test my WPF databindings using the test suit provided by Microsoft Team System. I would like to be able to test the bindings without showing the window because most of my tests will be for user controls and not actually on a window. Is this possible or is there a better way to do it? The code below works if I show the window, but if I don't, the bindings don't update.
Window1_Accessor target = new Window1_Accessor();
UnitTestingWPF.Window1_Accessor.Person p = new UnitTestingWPF.Window1_Accessor.Person() { FirstName = "Shane" };
Window1 window = (target.Target as Window1);
window.DataContext = p;
//window.Show(); //Only Works when I actually show the window
//Is it possible to manually update the binding here, maybe? Is there a better way?
Assert.AreEqual("Shane", target.textBoxFirstName.Text); //Fails if I don't Show() the window because the bindings aren't updated
While looking for a solution to convert WPF binding errors into exception, I figured out that it can also be used in a unit test project.
The technique is very simple:
Derive a TraceListener that throws instead of logging
Add that listener to PresentationTraceSources.DataBindingSource
Please see the complete solution on GitHub, it includes a unit test project.
Shane, if what you're really worried about is a binding breaking silently, you should look at redirecting the binding traces to somewhere you can examine. I'd start here:
http://blogs.msdn.com/mikehillberg/archive/2006/09/14/WpfTraceSources.aspx
Other than that, I agree with Gishu that bindings aren't good candidates for unit testing, mainly due to the automagic going on that Gishu mentioned in the "Epilogue". Instead focus on making sure the underlying class behaves correctly.
Note, too, that you can get even more robust traces using the PresentationTraceSources class:
http://msdn.microsoft.com/en-us/library/system.diagnostics.presentationtracesources.aspx
Hope that helps!
Eyeball it.
This kind of declarative markup rarely breaks.. unless someone goes in manual and screws it up. Even then, you can fix it within minutes. IMHO the cost of writing such tests far outweigh the benefits.
Update[Dec3,08]: Alrighty then.
The test is just testing that the textbox has the value "FirstName" as the Path property of the binding. If I change/refactor FirstName to JustName in the actual data source object, the test would still pass since it is testing against an anonymous type. (Green test when code broken - TDD Antipattern: The Liar)
If your aim is to verify that FirstName has been specified in XAML,
Assert.AreEqual("FirstName", txtBoxToProbe.GetBindingExpression(TextBox.TextProperty).ParentBinding.Path.Path);
If you really must catch broken bindings via unit tests (and don't want to show the UI), use the real data source... struggled for a while and came up with this.
[Test]
public void TestTextBoxBinding()
{
MyWindow w = new MyWindow();
TextBox txtBoxToProbe = w.TextBox1;
Object obDataSource = w; // use 'real' data source
BindingExpression bindingExpr = BindingOperations.GetBindingExpression(txtBoxToProbe, TextBox.TextProperty);
Binding newBind = new Binding(bindingExpr.ParentBinding.Path.Path);
newBind.Source = obDataSource;
txtBoxToProbe.SetBinding(TextBox.TextProperty, newBind);
Assert.AreEqual("Go ahead. Change my value.", txtBoxToProbe.Text);
}
Epilogue:
There's some real covert stuff happening in the call to Window.Show(). It somehow magically sets up the DataItem property after which data binding starts working.
// before show
bindingExpr.DataItem => null
bindingExpr.Status => BindingStatus.Unattached
// after show
bindingExpr.DataItem => {Actual Data Source}
bindingExpr.Status => BindingStatus.Active
Once the Binding is Active, I guess you can force textbox updates via code like this..
txtBoxToProbe.GetBindingExpression(TextBox.TextProperty).UpdateTarget();
Once again, I voice my reluctance against this approach. Getting NUnit to run in STA was a pain..
Combining advice I came across in a number of SO posts I wrote the following class which works very well to test WPF bindings.
public static class WpfBindingTester
{
/// <summary>load a view in a hidden window and monitor it for binding errors</summary>
/// <param name="view">a data-bound view to load and monitor for binding errors</param>
public static void AssertBindings(object view)
{
using (InternalTraceListener listener = new InternalTraceListener())
{
ManualResetEventSlim mre = new ManualResetEventSlim(false);
Window window = new Window
{
Width = 0,
Height = 0,
WindowStyle = WindowStyle.None,
ShowInTaskbar = false,
ShowActivated = false,
Content = view
};
window.Loaded += (_, __) => mre.Set();
window.Show();
mre.Wait();
window.Close();
Assert.That(listener.ErrorMessages, Is.Empty, listener.ErrorMessages);
}
}
/// <summary>Is the test running in an interactive session. Use with Assume.That(WpfBindingTester.IsAvailable) to make sure tests only run where they're able to</summary>
public static bool IsAvailable { get { return Environment.UserInteractive && Process.GetCurrentProcess().SessionId != 0; } }
private class InternalTraceListener : TraceListener
{
private readonly StringBuilder _errors = new StringBuilder();
private readonly SourceLevels _originalLevel;
public string ErrorMessages { get { return _errors.ToString(); } }
static InternalTraceListener() { PresentationTraceSources.Refresh(); }
public InternalTraceListener()
{
_originalLevel = PresentationTraceSources.DataBindingSource.Switch.Level;
PresentationTraceSources.DataBindingSource.Switch.Level = SourceLevels.Error;
PresentationTraceSources.DataBindingSource.Listeners.Add(this);
}
public override void Write(string message) {}
public override void WriteLine(string message) { _errors.AppendLine(message); }
protected override void Dispose(bool disposing)
{
PresentationTraceSources.DataBindingSource.Listeners.Remove(this);
PresentationTraceSources.DataBindingSource.Switch.Level = _originalLevel;
base.Dispose(disposing);
}
}
}
you can try Guia.
With it you can unit-test your UserControl and check if the data binding is correct. You have to show the window though.
Here is an example. It starts a new instance of your UserControl and sets its DataContext and then checks if the textbox is set to the right value.
[TestMethod]
public void SimpleTest()
{
var viewModel = new SimpleControlViewModel() {TextBoxText = "Some Text"};
customControl = CustomControl.Start<SimpleUserControl>((control) => control.DataContext = viewModel);
Assert.AreEqual("Some Text", customControl.Get<TextBox>("textbox1").Value);
customControl.Stop();
}