What exactly I want to do is that there are 2 tables,ie, user and userprofile and both of them have almost identical fields. I shall take example of the email field. There is a textbox and the User table email field value is displayed in it. What I want to do is, have a context menu such that when the user right clicks on the textbox, the menu displays both the User and UserProfile email field values. – developer 1 hour ago
Whatever value one selects from the context menu the textbox then displays that value. You can use Binding Email1 and Binding Email2, as I have no problems getting those two values from database so I shall change my code accordingly. As I am new to WPF and .NET framework itself, I am not sure how to achieve this. Please let me know if I have made myself clear this time.
I am not sure how to handle commands and events. Can anybody show me the code to accomalish this..
<TextBox Style="{StaticResource FieldStyle}" Text="{Binding Email1, UpdateSourceTrigger=PropertyChanged}">
<TextBox.BorderBrush>
<MultiBinding Converter="{StaticResource TextBoxBorderConverter}">
<Binding Path="Email1"/>
<Binding Path="Email2"/>
</MultiBinding>
</TextBox.BorderBrush>
</TextBox>
Thanks in advance
At risk of giving you a WPF/MVVM noob answer and getting flamed, here goes. I can't advise you on databinding with databases since I've never done it, so I will just give you the XAML and it's up to you to work on the database end.
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid>
<TextBox Height="28" Text={Binding PreferredEmail}">
<TextBox.ContextMenu>
<ContextMenu>
<MenuItem Header="{Binding Email1}" Command="{Binding Email1Command}" />
<MenuItem Header="{Binding Email2}" Command="{Binding Email2Command}" />
</ContextMenu>
</TextBox.ContextMenu>
</TextBox>
</Grid>
</Page>
In the databinding to objects case, PreferredEmail, Email1, and Email2 would bind to a dependency property or a property that raises the PropertyChanged event. This is how your ViewModel (or whatever you want to call the lower-level code) will update the data. If you change those values in code-behind, ultimately it'll get reflected in the context menu automagically. Then you have to implement two ICommand-based classes to handle the setting of PreferredEmail.
I think it's super lame to implement two command handlers, and it certainly won't scale well if you have to add more email sources. I think a better solution would be to use one command handler and a CommandParameter that is the selected MenuItem header, but I don't know how to do that. But in any case, the two command handler solution will still work if you're in a bind.
Related
Sorry for my bad headline but I couldn't figure out a better one. Heck, I don't even know how to properly ask my question. But here it comes.
I have a custom control in WPF, let's call it Cell. This control does have a few dependency properties, one Text to show in the Cell and a few "decorative" properties for background color, foreground color and so on. If I use this Cell control stand-alone, everything works fine so far.
Then I have another custom control inheriting from ItemsControl, let's call it Field. This control should show a text and some Cells. it has some "decorative" properties for the text part as well. The information about showing Cells is given to the control by a DataTemplate, something like
<DataTemplate x:Key="CellTemplate"
DataType="...">
<ns:Cell Text="{Binding Text}"
Background="{Binding ...}" />
</DataTemplate>
...
<ns:Field ItemsSource="{Binding Cells}"
ItemTemplate="{StaticResource CellTemplate}" />
If I use this Field control stand-alone, everything works fine so far.
Now I want to show several Field controls at once. So I put an ItemsControl on my window and gave an ItemTemplate again, something like:
<DataTemplate x:Key="CellTemplate"
DataType="...">
<ns:Cell Text="{Binding Text}"
Background="{Binding ...}" />
</DataTemplate>
<DataTemplate x:Key="FieldTemplate"
DataType="...">
<ns:Field ItemsSource="{Binding Cells}"
ItemTemplate="{StaticResource CellTemplate}"
FieldText="{Binding Text}"
TextBackground="{Binding ...}" />
</DataTemplate>
<ItemsControl ItemsSource="{Binding Fields}"
ItemTemplate="{StaticResource FieldTemplate}" />
As long as I preview my WPF window everything works fine so far. Changing the values of some "decorative" properties at Cell level or at Field level is immediately shown in the preview.
But if I run my program it seems that all "decorative" properties at Cell level are ignored. I can see all my Fields with their respective texts and I can see every Cell in every Field with their respective texts. But all Cells are plain white. All set colors are not shown.
Snoop tells me, that every color is set to Transparent by the ParentTemplate.
Visual Studio doesn't show me any exceptions or any binding errors. So I'm kind of stuck at where or how I can find the error and fix it.
So I wanted to ask you, if you may have a hint for me.
Does this contruction with a DataTemplate containing a DataTemplate and both DataTemplates bind to it's DataContext work?
Or does it have something to do with maybe re-using Brush objects that shouldn't be re-used?
But why is it working in the preview?
I'm new to WPF. Currently working on a sample app with MVVM pattern. I have a ListView which is populating three columns (Id, Name, Edit).
Here, whenever user clicks on Edit button, he would be redirected to "Edit form" with pre-populated values (Selected item in ListView).
Edit button is bound to ICommnad and im passing SelectedItem as CommandParameter.
My problem is whenever ICommand fires it contains the previously selected item as SelectedItem.
Any idea how to solve this?
You can find source code at: https://github.com/4pawan/WPF_Sample
The problem is that the button command handler is called before the binding engine has had a chance to update the SelectedItem property.
First of all you've got some architectural problems. Putting NavigateToForm in ithe EmpFormViewModel is poor SoC and I suspect you've only done it to make the binding easier to declare. It should really be in the parent EmpViewModel and of type RelayCommand<EmpFormViewModel>:
NavigateToForm = new RelayCommand<EmpFormViewModel>(vm =>
{
this.IsImportDataVisible = false;
this.IsSearchVisible = true;
//do something with vm here
});
Then all you have to do is modify your button command binding to bind to the parent instead and pass in the list item. So replace all of this...
<Button Content="Edit" Command="{Binding NavigateToForm}">
<Button.CommandParameter>
<MultiBinding Converter="{StaticResource EditEmpConverter }">
<!--<Binding Path="DataContext" ElementName="mainWindow"/>-->
<Binding Path="SelectedItem" ElementName="LstVw"/>
</MultiBinding>
</Button.CommandParameter>
</Button>
...with this:
<Button Content="Edit" Command="{Binding RelativeSource={RelativeSource AncestorType=ListView}, Path=DataContext.NavigateToForm}" CommandParameter="{Binding}" />
Note that I've also removed the converter from the equation, if you really do need a cloned instance then do it in the ViewModel handler where it can at least be more easily tested. Converters are a powerful tool but they're often abused to compensate for poor binding between view model and views. It's the primary responsibility of the view model to present the data in a form that can be easily consumed by the view, if you find yourself relying on them too much or for very simple tasks (such as the case here) then it's often a good indication that the view model isn't doing its job properly.
I have a simple control that has a masked text box:
xmlns:extToolkit="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit/extended"
...
<extToolkit:MaskedTextBox Mask="000-000-000" Text="{Binding SerialNumber, UpdateSourceTrigger=PropertyChanged}" />
I also have a key binding on the control:
<UserControl.InputBindings>
<KeyBinding Command="{Binding SearchCommand}" Gesture="Enter" />
</UserControl.InputBindings>
The problem is when SearchCommand is executed I need the value they entered in the masked text box as the criteria for the search. With a regular text box this is no problem but apparently the MaskedTextBox control doesn't play well with PropertyChanged UpdateSourceTrigger.
If I click someplace else (so it looses focus) and then press enter it works, but obviously I don't want to have to do that. Are there any good workarounds for this situation?
You must bind your property to the Value property not the Text.
http://wpftoolkit.codeplex.com/wikipage?title=MaskedTextBox&referringTitle=Documentation
I have an ObservableCollection of addresses that I am binding to a ListBox. Then in the ItemTemplate I am Binding to the current address record using {Binding .}. This results in my addresses displaying using their ToString method which I have setup to format the address. All is good, except if I update properties on an individual address record the list in the UI does not update. Adds/Deletes to the list do update the UI (using the ObservableCollection behavior). If I bind directly to properties on the address the UI does update (using the INotifyPropertyChanged behavior of the Address object).
My question is, is there a way to notify the UI of the change to the object as a whole so that I can still use this syntax or do I need to punt and put a DisplayText property on my address type that calls the ToString method and bind to that? FYI, this is an MVVM architecture so I don't have the luxury of calling Refresh on the ListBox directly.
Thanks for any help/ideas.
<ListBox x:Name="AddressList" ItemsSource="{Binding Addresses}" Background="Transparent" BorderBrush="Transparent"
Width="200" HorizontalAlignment="Left">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding .}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
When you bind to the Address object itself, the object itself -- that is, its identity -- doesn't change, even though its properties do. WPF therefore doesn't know to refresh the binding in this case.
So yes, you need to bind to a notifying property (or properties) rather than the whole object. As you say, one way to do this is to create a DisplayText property, and raise the PropertyChanged event for that property whenever something that affects the display text changes. Another is to use multiple TextBlocks in a horizontally oriented StackPanel, each bound to a particular property e.g.
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding HouseNumber}" />
<TextBlock Text=", " />
<TextBlock Text="{Binding Street}" />
<TextBlock Text=", " />
<TextBlock Text="{Binding City}" />
</StackPanel>
The advantage of the second approach is that it gives you flexibility in the UI to change how addresses are displayed, e.g. multiple lines, formatting, etc.; the downside is that it gets complicated if you have conditional logic e.g. an optional flat number or second address line.
I tried to reproduce the problem and succeeded.
I activated the step-into-.NET debugging options, and saw that WPF does not listen to INotifyPropertyChanged if the path in the binding is empty.
What worked to get a change to be reflected in the list box is to replace the whole object in the ObservableCollection. This triggers the INotifyCollectionChanged, with the Replace action.
But this may not be acceptable in your case. And it could be seen more like a hack than a solid solution.
I'd seriously consider having a DataTemplate for Address. There you should bind to the exact properties you need (which would create the listener for INotifyPropertyChanged). It is more flexible than ToString() and you may encounter cases where you have a need for ToString() to do something for non-UI stuff, which would create a conflict. And honestly, ToString is not really meant for UI stuff.
I'd like an advice to the following problem: I want to embed a Button into a text flow, but when I embed a Button and Label (or TextBlock) into the WrapPanel, I get the first figure:
alt text http://sklad.tomaskafka.com/files/wpf-wrappanel-problem.png
I think that one of solutions could be FlowDocument, but I feel that this is far too heavy for a control simple like this (which could be used in several hundred instances). Do you have some other ideas about how to implement this? Thank you!
EDIT:
One solution could be the following (I didn't know it was possible to put more stuff into TextBlock), but I would lose the ability to bind (which I need):
<TextBlock TextWrapping="Wrap">
<Span>
<Button x:Name="MyButton" Command="{Binding Path=MyCommand}" Content="+" />
<Run x:Name="MyLabel" Text="{Binding Path=Subject}" />
<!--
Problem: binding makes following error:
A 'Binding' cannot be set on the 'Text' property of type 'Run'.
A 'Binding' can only be set on a DependencyProperty of a DependencyObject.
-->
</Span>
</TextBlock>
To bind to Run.Text, checkout the BindableRun class by Fortes. Simple to implement, I use it all over my projects.
I found that implementing BindableRun correctly is pretty tricky - and almost all other available implementations will cause an exception from wpf layouting engine when the bound content changes from null to something non-null - see this problem, keyword "Collection was modified; enumeration operation may not execute."
Corrrect implementation from Microsoft is here - it shows how tricky this really is.
Solution: BindableRun class + the following markup:
<TextBlock>
<Button x:Name="MyButton" Command="{Binding Path=MyCommand}" Content="+" />
<common:BindableRun x:Name="Subject" BindableText="{Binding Path=Subject}"/>
</TextBlock>
Funny thing it works on the designer of a UserControl...
In that case, using the Property Change of your control to set the value to the Run is enough. I mean, if you had something like:
<TextBlock>
<Run Text="{Binding ElementName=thisCtrl, Path=Description}" />
</TextBlock>
Then just name the run, and on your property change handler of your UserControl DependencyProperty get/set the value.