I have the following problem:
there is a class with a couple of string properties
there is a collection of such class entities
That collection is shown in tree on the left of some windows and details shown on the right. I'm binding string properties of selected node to comboboxes in details.
First combobox always have the same ItemsSource but the second one ItemsSource depends on SelectedItem of the first combo...
<ComboBox
Grid.Column="1"
SelectedIndex="0"
x:Name="cbClass"
Style="{DynamicResource ComboBoxValidationError}"
SelectedValue="{Binding Path=Description.Node.ClassName, ElementName=userControl, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding Source={StaticResource classesProvider}}"
Width="Auto"
Height="Auto"
DisplayMemberPath="Description"
SelectedValuePath="FQN" />
<ComboBox
Grid.Column="1"
SelectedIndex="0"
Grid.Row="1"
x:Name="cbMethod"
SelectedValue="{Binding Path=Description.Node.MethodName, ElementName=userControl, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged,diag:PresentationTraceSources.TraceLevel=High}"
ItemsSource="{Binding Path=SelectedItem.Methods, ElementName=cbClass, Mode=Default,diag:PresentationTraceSources.TraceLevel=High}"
Style="{DynamicResource ComboBoxValidationError}"
Width="Auto"
Height="Auto"
SelectedValuePath="Name"
DisplayMemberPath="Description" />
Now when i create new node in the tree, both string properties have null reference. And when first combo changes its SelectedItem for the NEW node, second ComboBox binds null to the string value of the OLD node, which were selected before creating new node in the tree... I wonder what should i do in this case?
I've just found an answer.
Binding are notified in the order of their declaration, WPF is not going to analyse dependencies of bindings :)
So swapping declarations of ComboBoxes solves the problem... It's acceptable in this scenario because I place these ComboBoxes in Grid manually setting their Grid.Row and Grid.Column...
Though solution is not very pleasing, it works!
Related
Solved problem, but still have questions. See end of post, or read on for context.
I'm trying to setup a WPF datagrid which has many templated columns with comboboxes inside of them. In particular I'm having trouble with data-binding.
Data Model
First, I have Entry, which contains 4 properties:
Name
Customer
Color
Type
The most interesting property is Color which has two more sub properties:
ColorString
Index
Goal
I need to create a data grid where each row corresponds to an Entry object. The Customer, Color, and Type properties all have comboboxes that allow for a selection of dynamically populated choices. I need the selected item for each combobox to bind to the entry's respective property.
Screenshot
Questions:
How do I properly set the data contexts for the data grid and for each combobox?
For the data grid, I'm setting the data context programmatically to an instance of ObservableCollection.
private ObservableCollection<Entry> entries = new ObservableCollection<Entry>();
public MainWindow()
{
InitializeComponent();
entries.Add(new Entry("Foo", "Customer1", new MyColor("#00000000", 1), "Type1"));
entries.Add(new Entry("Bar", "Customer2", new MyColor("#00000000", 1), "Type2"));
LayerMapGrid.DataContext = entries; //Set data-context of datagrid
}
For the color combobox, I'm using an ObjectDataProvider in my XAML:
<Window.Resources>
<ObjectDataProvider x:Key="Colors" ObjectType="{x:Type local:MyColor}" MethodName="GetColors"/>
</Window.Resources>
This is how I bind the ObjectDataProvider
<ComboBox ItemsSource="{Binding Source={StaticResource Colors}}"/>
In the MyColor class, I've created the method below:
public static ObservableCollection<MyColor> GetColors()
{
ObservableCollection<MyColor> colors = new ObservableCollection<MyColor>();
//... Fill collection... (omitted for brevity)
return colors;
}
The good news is that ALL of the above code WORKS. However is it a good approach to the problem at hand?
This my next and more important question:
How do I bind the selected items of the comboboxes so that ObservableCollection<Entry> is updated?
I'm aware that I need to set the UpdateSourceTrigger="PropertyChanged", so that my source, which is the Entry collection is updated.
Here is my current XAML code for setting up my entire data grid. Note: I haven't implemented the customer and type comboboxes yet. I'm really just concerned with the color combobox:
<DataGrid ItemsSource="{Binding}" AutoGenerateColumns="False" Name="LayerMapGrid">
<DataGrid.Columns>
<!--Name Column-->
<DataGridTemplateColumn Header="Name">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Label Content="{Binding Name, UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
<DataGridTemplateColumn.HeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="Control.HorizontalContentAlignment" Value="Center" />
</Style>
</DataGridTemplateColumn.HeaderStyle>
</DataGridTemplateColumn>
<!--Customer Column-->
<DataGridTemplateColumn Header="Customer">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox SelectedItem="{Binding CustomerName, UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<!--Color Column-->
<DataGridTemplateColumn Header="Color">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Source={StaticResource Colors}}" SelectedItem="{Binding Color, ElementName=LayerMapGrid, UpdateSourceTrigger=PropertyChanged}">
<ComboBox.ItemTemplate>
<DataTemplate>
<DockPanel Margin="2">
<Border DockPanel.Dock="Left" HorizontalAlignment="Right" BorderThickness="1" BorderBrush="Black" Margin="1" Width="10" Height="10">
<Rectangle Name="ColorRec" Fill="{Binding ColorString}"/>
</Border>
<TextBlock Padding="4,2,2,2" Text="{Binding ColorString}" VerticalAlignment="Center"/>
</DockPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<!--Type Column-->
<DataGridTemplateColumn Header="Type">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox SelectedItem="{Binding Type, UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
Your assistance is greatly appreciated. I've been banging my head on the wall for about 16 hours with this.
-Nick Miller
EDIT:
I found the solution (and as always immediately after requesting help), but I don't understand how it works.
In the XAML, I've changed the combobox binding to be the following:
<ComboBox ItemsSource="{Binding Source={StaticResource Colors}}" SelectedItem="{Binding Color, UpdateSourceTrigger=PropertyChanged}">
What exactly is happening here?
Why is the combobox now referring to the datagrid's data context? Doesn't that get overriden when I set the ItemsSource to point to my ObjectDataProvider?
How do I properly set the data contexts for the data grid and for each combobox?
You don't. Normally in WPF, we set the DataContext property on the UserControl, or Window that we are designing, not on individual controls. In this way, all the controls in the view have access to the data properties.
How do I bind the selected items of the comboboxes so that ObservableCollection is updated?
Again, you don't do what you are doing. Rather than using an ObjectDataProvider, you should just have a property of type ObservableCollection<MyColor> in the code behind and bind to that directly. And you should be binding a public Entries property to the DataGrid.ItemsSource property, not setting the private entries field as the DataContext. You really need to read through the Data Binding Overview page on MSDN for further help with this.
Set the DataContext of MainWindow.xaml to itself (which generally is a not a good idea):
public MainWindow()
{
InitializeComponent();
Entries.Add(new Entry("Foo", "Customer1", new MyColor("#00000000", 1), "Type1"));
Entries.Add(new Entry("Bar", "Customer2", new MyColor("#00000000", 1), "Type2"));
DataContext = this; //Set DataContext to itself so you can access properties here
}
Then in MainWindow.xaml:
<DataGrid ItemsSource="{Binding Entries}" ... />
The DataTemplates in each row of the DataGrid automatically have the relevant item in the data bound collection set as the DataContext, so you automatically get access to the properties from the relevant class. Again... no need to set any DataContexts manually. If you have further questions, please read the linked article, because the answers are there.
UPDATE >>>
Let's be clear about something... I am not your personal mentor, so this will be my last reply.
How do I overcome the combobox inheriting the data context of the data grid?
To data bind to the object that is set as the Window.DataContext, you just need to use a valid Binding Path and some basic logic:
<ComboBox ItemsSource="{Binding DataContext.MyColors, RelativeSource={RelativeSource
AncestorType={x:Type YourLocalPrefix:MainWindow}}}" />
Here is a snippet of XAML:
<ComboBox ItemsSource="{Binding UnileverDataSet.Tables, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" Margin="5" x:Name="TableNameComboBox">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding TableName}"></TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
<DataGrid Margin="5" AutoGenerateColumns="True" ItemsSource="{Binding UnileverDataSet.Tables[TableNameComboBox.SelectedIndex]}"
UnileverDataSet is a DataSet made up of about 12 DataTables
The idea here is that when the ComboBox value changes, the DataGrid should update based on the index value from the ComboBox.
Is this possible or should I look at another way of doing this?
If I do: UnileverDataSet.Tables[0], then all works and data displays correctly.
You can do element binding with combobox..
Your combox will display list of items in the "UnileverDataSet.Tables" collection. When ever your select a item in Combo box the selected item will bounded to the Datagrid Items source (since we are using element binding)
Here is the sample code
<DataGrid Margin="5" AutoGenerateColumns="True" ItemsSource="{Binding SelectedItem,ElementName=TableNameComboBox}">
I am writing what is turning out to be a simple GUI in WPF. At the moment I have a static list inside of a ComboBox, like this:
<ComboBox HorizontalAlignment="Left" Height="22" Margin="24,97,0,0" VerticalAlignment="Top" Width="83"
SelectedItem="{Binding fruit, Mode=TwoWay}">
<ComboBoxItem>apple</ComboBoxItem>
<ComboBoxItem>orange</ComboBoxItem>
<ComboBoxItem>grape</ComboBoxItem>
<ComboBoxItem>banana</ComboBoxItem>
</ComboBox>
I'm binding the SelectedItem to a singleton in my code that has already been initialized and used elsewhere.
I put a breakpoint on the get of fruit and it returns "grape", but the selected item is always blank. I even added a button so that I could call RaisePropertyChanged manually, but the RaisePropertyChange call didn't do anything either.
Finally, MVVMLight gives blendability. For no important reason I changed the binding in the combobox from SelectedItem to Text As soon as I did that, my design time form filled in with the expected values, but, when the code is running, the box continues to sit at the empty state
This is because you have items of type ComboBoxItem in the ComboBox but the property you are trying to bind to is of type string.
You have three options:
1.Instead of adding ComboBoxItem items add String items:
<ComboBox HorizontalAlignment="Left" Height="22" Margin="24,97,0,0" VerticalAlignment="Top" Width="83"
SelectedItem="{Binding fruit, Mode=TwoWay}">
<sys:String>apple</sys:String>
<sys:String>orange</sys:String>
<sys:String>grape</sys:String>
<sys:String>banana</sys:String>
</ComboBox>
2.Instead of SelectedItem bind to SelectedValue and specify SelectedValuePath as Content:
<ComboBox HorizontalAlignment="Left" Height="22" Margin="24,97,0,0" VerticalAlignment="Top" Width="83"
SelectedValue="{Binding fruit, Mode=TwoWay}"
SelectedValuePath="Content">
<ComboBoxItem>apple</ComboBoxItem>
<ComboBoxItem>orange</ComboBoxItem>
<ComboBoxItem>grape</ComboBoxItem>
<ComboBoxItem>banana</ComboBoxItem>
</ComboBox>
3.Do not specify items directly in XAML, but use ItemsSource property to bind to a collection of strings:
<ComboBox HorizontalAlignment="Left" Height="22" Margin="24,97,0,0" VerticalAlignment="Top" Width="83"
ItemsSource="{Binding Fruits}"
SelectedItem="{Binding fruit, Mode=TwoWay}"/>
You should bind ComboBox.ItemSource to a list of strings (make the List of strings an ObservableCollection<string> in case you add items to this list) and then set the fruit variable to an instance in the List of strings.
I think you have your problem because your fruit variable references a different instance than you have in your list of ComboBoxItems. (even though the strings are the same)
<UserControl.Resources>
<DataTemplate x:Key="LstBoxTemplate">
<TextBlock Text="{Binding Item}" TextWrapping="Wrap" HorizontalAlignment="Left"/>
<Image Grid.Column="2" Margin="0,0,10,0" Visibility="{Binding isVisible,Converter={StaticResource ImageCtlVisibilityConverter}}" Source="/pjct;component/Images/im.png"/>
</DataTemplate>
</UserControl.Resources>
<ListBox x:Name=lstbox ItemsSource="{Binding itemList}" ItemTemplate="{StaticResource LstBoxTemplate}" />
You question needs more detail, and so I may be missing the point...
If your listbox is bound to a collection of custom objects that you control (aka a view model). Then it should be fairly straight forward for you to add a property to the view model that contains the object that you want to bind your listboxitem to...
Why is the first element in my combobox popup menu not shown in the selected item area of
my combobox , when I use the SelectedItem binding? Without that it is showing up ?? Using
the same code selecteditem + selectedindex that is no problem!
<ComboBox
ItemsSource="{Binding SchoolclassSubjectViewModels}"
SelectedItem="{Binding SelectedSchoolclassSubjectViewModel}"
SelectedIndex="0"
Height="23"
HorizontalAlignment="Left"
Margin="375,13,0,0"
VerticalAlignment="Top"
Width="151">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding SchoolclassName}" />
<TextBlock Text=" " />
<TextBlock Text="{Binding SubjectName}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
Well as workaround I used:
SchoolclassSubjectViewModels.Add(schoolclassSubjectVM);
SelectedSchoolclassSubjectViewModel = schoolclassSubjectVM;
and this:
SelectedItem="{Binding SelectedSchoolclassSubjectViewModel,Mode=TwoWay}"
but I would prefer the xaml only way as it should really work.
It is because the reference inside your ItemsSource collection is not the same as the one in your SelectedItem property. I would venture to guess that you are using one object context to query your database for the list of SchoolclassSubject objects which the ItemsSource is bound to, but another context to query the actual data item to which you bind the SelectedItem. Even though the list contains a reference which represents the value held by your object, it is not really the same reference, but a separate instance of the same data.
There are ways to solve this issue, most of them involve using the SelectedValuePath and SelectedValue instead of the SelectedItem properties, but the concrete solution would be different depending on your particular ORM.