I have a problem trying to bind a DataGrid to a List, or to a Dictionary.
If I set DataContext to an object, and set ItemSource to a List property of that object, I get DataGrid populated with List count, in case of a List, why? How can I bind properly to a List, and how to a Dictionary?
List<string> con = new List<string>();
con.Add("aaaddd");
con.Add("bbb");
this.DataContext = con;
<DataGrid AutoGenerateColumns="True" Height="104" HorizontalAlignment="Left" Margin="34,171,0,0" Name="dg" VerticalAlignment="Top" Width="421" ItemsSource="{Binding}"/>
And I get populated with
Length
6
3
Why? And how to bind to a Dictionary?
Problem is you have set AutoGenerateColumns to True on your dataGrid.
When AutoGenerateColumns is set to true than columns are auto generated based on the properties exposed by the underlying object which is in your case is string which only exposes single property i.e. Length.
In case you want to get the value of string, you need to set that property to false and provide your own columns collection. This will work -
<DataGrid ItemsSource="{Binding}" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Header="Value"
IsReadOnly="True"
Binding="{Binding}"/>
</DataGrid.Columns>
</DataGrid>
As said in the comment, I think you're refering to WPF's DataGrid Control.
If you're setting the list object to the DataContext then just ItemsSource="{Binding}" this will bind to the DataContext root which is your list object.
Related
I a have a View Players, the datacontext is set to a ObservableCollection Players from the ViewModel MainPlayerViewModel.
In the View I have a datagrid with columns TeamId, Name and Position.
I want to bind the TeamId column with a combobox to a list of available teams from the MainTeamViewModel which has a collection property Teams but of course I want the MainPlayerViewModel to be updated whenever I update the team for a player.
I hope you can follow me here..
This is my xaml:
<data:DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ComboBox DataContext="{Binding MainTeam, Mode=OneWay, Source={StaticResource Locator}}"
Height="23" HorizontalAlignment="Left"
Name="cmbTeams" VerticalAlignment="Top" Width="100" ItemsSource="{Binding Teams,
Mode=TwoWay}" SelectedValue="{Binding Path=Model.teamid, Mode=TwoWay}"
DisplayMemberPath="Model.teamid"/>
</DataTemplate>
</data:DataGridTemplateColumn.CellEditingTemplate>
When I edit the cell it shows the list of available teams but the selectedvalue I pick from the list doesn't turn up in the TeamId column
How do I pull this off?
Kind regards,
Mike
UPDATE:
Despite the help I received I didn't get it to work binding one View to 2 different Viewmodels.
Guess the solution offered is long above my head..
I couldn't set the datacontext of the datagrid to MainTeam because it has an ItemsSource of players and a selecteditem bound twoway to selectedplayer.
Anyway I decided to keep it 1 View / 1 ViewModel and created a public property on my PlayerViewModel named teamsVM:
public MainTeamViewModel teamsVM
{
get
{
return ViewModelLocator.Container.Resolve<MainTeamViewModel>();
}
}
Now I can set the Itemsource to this new property and my player row get's updated when I change teams:
<DataTemplate>
<ComboBox
Height="23" HorizontalAlignment="Left"
Name="cmbTeams" VerticalAlignment="Top" Width="100"
ItemsSource="{Binding teamsVM.Teams,
Mode=TwoWay}" SelectedValue="{Binding Model.teamid, Mode=TwoWay}"
DisplayMemberPath="Model.teamid" SelectedValuePath="Model.teamid"/>
</DataTemplate>
Regards,
Mike
I find two things wrong with this code.
You are missing the SelectedValuePath for the ComboBox. Even though you bind all teams to it, the selected item's id is null because the SelectedValuePath is missing.
You also have a DataContext and an ItemsSource. Use only the ItemsSource for the teams you want to display, and the SelectedValue to be bound to the player's teamId, unless your view model has a "Teams" property and a "Player" property, in which case the DataContext may be used. (Id set the DataContext in code though...)
So yo will end up with something like this:
ItemsSource="{Binding Teams, Mode=TwoWay}" //Bind to all teams.
SelectedValue="{Binding Player, Path=TeamId, Mode=TwoWay}" //Bind to the teamId of the player.
DisplayMemberPath="TeamName" //that's the Name of each team.
SelectedValuePath="TeamId" //that's the Id of the team.
Two problems here:
First, as #bleepzer noted you did not specify the value/display paths in your combo box.
Second, you trying to access a property in the data context that is outside your grid (i.e. the main view model's data context) from within a data template. In silverlight 4 there is no relative source binding (something you would use in SL 5 or WPF), so you will have to use element binding to archive what you want.
Here is an example based on your code. It is not complete as it leaves out some of the DataGrid elements needed, but it shows the concept:
<data:DataGrid x:Name="myDataGrid"
DataContext="{Binding MainTeam, Mode=OneWay, Source={StaticResource Locator}}" >
<!-- additional stuff needed here -->
<data:DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ComboBox Height="23" HorizontalAlignment="Left"
Name="cmbTeams" VerticalAlignment="Top" Width="100"
ItemsSource="{Binding ElementName=myDataGrid, Path=DataContext.Teams}"
SelectedValuePath="TeamId"
DisplayMemberPath="TeamName"
SelectedValue="{Binding Path=Model.teamid, Mode=TwoWay}"/>
</DataTemplate>
</data:DataGridTemplateColumn.CellEditingTemplate>
<!-- additional stuff needed here -->
<data:DataGrid>
And here is the description:
Add a name to your data grid.
Make sure the data grid has the right data context, either by setting it explicitly as in the sample, or inheriting it from the parent hierarchy.
Modify your ComboBox's ItemsSource property to point to the data grid using the element name you specified earlier. As you are now on the element and not on the data context you have to use DataContex.Teams to access the Teams property on the data context of your grid. The ItemsSource does not need two-way-binding as the view does not write anything back to your view model.
Specify the SelectedValuePath and DisplayMemberPath properties.
Finally, bind the SelectedValue property of the combo box to your rows model TeamId property using two-way-binding - needed now as the view should update the model's value. Important: the SelectedValue property of the combo box has to be bound after the ItemsSource to prevent some problems with the combo box.
I have two ComboBoxes
<ComboBox Name="cmbMake" DisplayMemberPath="MakeName" SelectedValuePath="MakeID"/>
<ComboBox Name="cmbModel" DisplayMemberPath="ModelName"/>
I use LINQ-to-Entities to populate the cmbGroup ComboBox
Dim db as myDataEntity
cmbGroup.ItemsSource = db.Makes
How do I populate my second ComboBox (cmbModels) based on the selection of the first ComboBox (cmbMake) using XAML so that whatever I select in the first ComboBox automatically filters the ItemsSource in the second ComboBox?
Is this even possible?
I am posting the full solution here
XAML
<ComboBox Name="cmbMake" DisplayMemberPath="MakeName" SelectedValuePath="MakeID" Width="200"/>
<ComboBox Name="cmbModel" DisplayMemberPath="ModelName" DataContext="{Binding SelectedItem, ElementName=cmbMake}" Width="200"/>
CODE-BEHIND
Private Sub cmbMake_SelectionChanged(ByVal sender As System.Object, ByVal e As System.Windows.Controls.SelectionChangedEventArgs) Handles cmbMake.SelectionChanged
Dim myItem = From m In myModel
Where m.MakeID = cmbMake.SelectedValue
cmbModel.ItemsSource = myItem
End Sub
Whenever the value is changed in the cmbModel ComboBox it will use LINQ to reset the ItemsSource of the cmbModel ComboBox.
Many Thanks to #XAMeLi for the helping hand!
If your data is hierarchical, where each item in db.Makes holds a list of the Models (and lets say this list is in a property called MyModelsList), then:
<ComboBox Name="cmbMake" DisplayMemberPath="MakeName" SelectedValuePath="MakeID"/>
<ComboBox Name="cmbModel" DisplayMemberPath="ModelName" DataContext="{Binding SelectedItem, ElementName=cmbMake}" ItemsSource="{Binding MyModelsList}"/>
It should be possible to use a converter to filter the items, for that you can employ a MultiBinding to get the values for the items and the selection in the other box in.
Would look something like this:
<ComboBox Name="cmbModel" DisplayMemberPath="ModelName">
<ComboBox.ItemsSource>
<MutliBinding>
<MultiBinding.Converter>
<vc:MyFilterConverter/>
</MultiBinding.Converter>
<Binding Path="Items"/> <!-- This should bind to your complete items-list -->
<Binding Path="SelectedValue" ElementName="cmbMake"/>
</MutliBinding>
</ComboBox.ItemsSource>
</ComboBox>
The converter needs to implement IMultiValueConverter.
My scenario:
I have a Telerik Silverlight RadGridView With some columns, and one of them is
<telerik:RadGridView x:Name="Grid1" DataContext="{StaticResource ViewModelDailyReport}" IsSynchronizedWithCurrentItem="True" ScrollMode="RealTime" AutoGenerateColumns="false" ItemsSource="{Binding LogBookItems}" IsReadOnly="false" Visibility="Visible" >
[...]
<telerik:GridViewComboBoxColumn
Header="My Activity"
DataMemberBinding="{Binding Activity.ID, Mode=TwoWay}"
SelectedValueMemberPath="ID"
DisplayMemberPath="Name"
ItemsSource="{StaticResource ViewModelActivities}">
</telerik:GridViewComboBoxColumn>
[...]
So I Have a TwoWay binding on a Collection of Items in a ViewModel.
All works fine, except when I insert a new item (with RadGrid BeginInsert command): when user chooses an item from the dropdown, it is always blank in the cell...
The bound collection has a new item (on insert event), but there is no way to bind the newly added item with combobox.
What is the trick?
Thanks
Make sure you have a default constructor in the LogBookItem class.
In the default constructor, you can initialize your default values and also create a new Activity instance, since you are binding to it's ID.
public LogBook()
{
//initialize default values
this.CreationDate = DateTime.UtcNow;
this.Activity = new Activity(); //Activity.ID will equal 0
}
I have a datagrid. A column of the datagrid is a simple <DataGridTemplateColumn> with its CellTemplate containing a <DataTemplate> which contains a <ComboBox> such as
<my:DataGrid Name="dataGridMain" AutoGenerateColumns="False">
<my:DataGrid.Columns>
<my:DataGridTemplateColumn Header="Food" >
<my:DataGridTemplateColumn.CellTemplate >
<DataTemplate>
<ComboBox Name="comboDataTemplate"
Text="{Binding Path=Food,
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding Source={StaticResource resFoodLookups}}"
DisplayMemberPath="FoodName"
SelectedValuePath="FoodID" IsEditable="True" />
</DataTemplate>
</my:DataGridTemplateColumn.CellTemplate>
</my:DataGridTemplateColumn>
</my:DataGrid.Columns>
</my:DataGrid>
All is working fine. Each combobox is bound to a static list due to the ItemsSource="{Binding Source={StaticResource resFoodLookups}}" statement.
But my requirement is that this list will change from row-to-row.
That is: each time a user types a new entry in the combobox list on one row, I want to have it available in the selection on the next row.
Basically, I want to create a new list for the user each time the user inserts a new word in the combobox on any of the rows. (The combobox is editable).
Now, I can wire up the "ItemsSource=..." at run-time, but I'm only able to do this once thus the <DataTemplate> propagates the 'same' list to 'all' the comboboxes on 'all' the rows.
My thoughts are that I need to change the ItemsSource=... property on an object-by-object basis on each combobox that is created in memory after the DataTemplate has created them - but I have no idea how to do this.
What you need to do is perform 2 way data binding to your the ItemsSource, this way when the ItemSource is updated in one of the combo boxes it will auto update your original collection and therefore your other combo boxes as well.
What I normally do is use the MVVM pattern. It is worth some research if you are not already using a particular pattern on your application.
Using it to solve your problem i would do the following:
Create a ViewModel (Lets call it MyViewModel) which has a collection of values called 'MyComboBoxItems' (It is important that you use ObservableCollection for the databinding to work)
When I create the Window/Control that contains your table, I also create an instance of MyViewModel and set its the Window.DataContext=myViewModelInstance
For your combobox binding use ItemsSource="{Binding Path=MyComboBoxItems, Mode=TwoWay}
In WPF Databinding, I understand that you have DataContext which tells an element what data it is going to bind to and ItemsSource which "does the binding".
But e.g. in this simple example it doesn't seem that ItemsSource is doing anything useful since, what else would you want the Element to do to the DataContext except bind to it?
<ListBox DataContext="{StaticResource customers}"
ItemsSource="{Binding}">
And in more complex examples of ItemsSource, you have Path and Source which seems to be encroaching on the territory of DataContext.
ItemsSource="{Binding Path=TheImages, Source={StaticResource ImageFactoryDS}}"
What is the best way to understand these two concepts as to know when and how to apply each of them in various coding scenarios?
DataContext is just a handy way to pick up a context for bindings for the cases where an explicit source isn't specified. It is inherited, which makes it possible to do this:
<StackPanel DataContext="{StaticResource Data}">
<ListBox ItemsSource="{Binding Customers}"/>
<ListBox ItemsSource="{Binding Orders}"/>
</StackPanel>
Here, Customers and Orders are collections on the resource called "Data". In your case, you could have just done this:
<ListBox ItemsSource="{Binding Source={StaticResource customers}}"/>
since no other control needed the context set.
ItemsSource property will be binded with collection object directly OR collection property of binding object of DataContext property.
Exp:
Class Root
{
public string Name;
public List<ChildRoot> childRoots = new List<ChildRoot>();
}
Class ChildRoot
{
public string childName;
}
There will be two ways to bind ListBox control:
1) Binding with DataContext:
Root r = new Root()
r.Name = "ROOT1";
ChildRoot c1 = new ChildRoot()
c1.childName = "Child1";
r.childRoots.Add(c1);
c1 = new ChildRoot()
c1.childName = "Child2";
r.childRoots.Add(c1);
c1 = new ChildRoot()
c1.childName = "Child3";
r.childRoots.Add(c1);
treeView.DataContext = r;
<TreeViewItem ItemsSource="{Binding Path=childRoots}" Header="{Binding Path=Name}">
<HierarchicalDataTemplate DataType="{x:Type local:Root}" ItemsSource="{Binding Path=childRoots}">
2) Binding with ItemSource:
ItemsSource property takes collection always.
here we have to bind collection of Root
List<Root> lstRoots = new List<Root>();
lstRoots.Add(r);
<HierarchicalDataTemplate DataType="{x:Type local:Root}" ItemsSource="{Binding Path=childRoots}">
In First example we have bind DataContext which has object inside that object we have collection which we binded with ItemSource property where in Second example we have directly bind ItemSource property with collection object.