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
}
Related
I'm using WPF and MVVM, and have a support ticket window that has cascading ComboBoxes as follows. The first is bound to an ObservableCollection<ProblemCode> on the view model. The ProblemCode objects have a self-referencing property to their child codes, down to a level of four codes. The XAML for the ComboBoxes looks like this (simplified, and only three shown for brevity)...
<ComboBox ItemsSource="{Binding ElementName=Root, Path=DataContext.ProblemCodes, Mode=TwoWay}"
Name="ProblemCodeLevel1"
DisplayMemberPath="Description"
SelectedValuePath="ID"
SelectedValue="{Binding ProblemCode1ID, Mode=TwoWay}" />
<ComboBox ItemsSource="{Binding ElementName=ProblemCodeLevel1, Path=SelectedItem.Children}"
Name="ProblemCodeLevel2"
DisplayMemberPath="Description"
SelectedValuePath="ID"
SelectedValue="{Binding ProblemCode2ID, Mode=TwoWay}" />
<ComboBox ItemsSource="{Binding ElementName=ProblemCodeLevel2, Path=SelectedItem.Children}"
Name="ProblemCodeLevel3"
DisplayMemberPath="Description"
SelectedValuePath="ID"
SelectedValue="{Binding ProblemCode3ID, Mode=TwoWay}" />
When I load a window for a new ticket, the first ComboBox is correctly populated. Selecting an item populates the second and so on. When I save the ticket, the data is correctly saved.
However, when I save the ticket and reopen the window, only the first ComboBox has the selected item set. The other ComboBoxes don't have anything set.
I guess that the first ComboBox is set as the data is available when the data binding takes place. At that stage, as the first ComboBox is data bound, the second one doesn't yet have any items, so doesn't get bound. Same for the third and so on.
Anyone any suggestions as to how to get the binding working? I probably could hack this by adding code to catch various events, but apart from breaking the MVVM pattern, it sounds like none of those situations that would end up convoluted and buggy.
Generally speaking you shouldn't bind directly to elements, you should be binding to properties in your view model. That way you know the property notification is being done properly and you can add breakpoints etc to confirm the bindings are all working as well. In this particular case you need to add something like SelectedItem="{Binding Level1Item}" to your first ComboBox and then add a property for it in your view model:
public ProblemCode _Level1Item;
public ProblemCode Level1Item
{
get { return this._Level1Item; }
set
{
if (this._Level1Item != value)
{
this._Level1Item = value;
RaisePropertyChanged(() => this.Level1Item);
}
}
}
Then your second ComboBox binds to this property instead of Element.SelectedItem.Children:
<ComboBox ItemsSource="{Binding Level1Item.Children}"
...etc...
Repeat for the second and third ComboBoxes and you'll have the functionality you're after.
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.
I'v a wizard style application that uses pages and the user can navigate between them either by Next and Previous buttons or by using a navigation bar to directely access certain pages.
On one page (i'll call it "grid page")i have a DataGrid bound to a DataTable. There is some initial data in the DataTable, but using the DataGrid the user can add, edit and delete rows as he wishes.
On the next page (i'll call i "combo box page") have a ComboBox which is bound to the same DataTable as the DataGrid on the grid page.
Both pages use the same object as data context.
If i jump to the combo box page directly everything works fine, the combo box has an entry for each row in the DataTable like it's supposed to be. Now i navigate to the grid page and don't touch anything there and then go to the combo box page again. Now the ComboBox displays a new item, a NewItemPlaceholder. Obviously this happens because the DataGrid has UserCanAddRows set to true and thus displays a placeholder row for a new item. But this should only concern the DataGrid and not the bound DataTable, so in my eyes this is a bug, or at least an absolutely horrible design.
Of course i don't want the NewItemPlaceholder in my ComboBox (and selecting it causes a lot of problems). So how can i prevent it from being displayed in the ComboBox?
Update: In the meantime i found out the placeholder item isn't in the DataTable as a row, which makes it even stranger, unless there is a flag in a DataTable that says "there is a NewItemPlaceholder in this table" but isn't a row itself. Additionally when i register to the Initialized event of the ComboBox i have the 2 items i'm looking for, when i register to the Loaded event i have the NewItemPlaceholder as well, so it must be added somewhere between those 2 events.
Use a CollectionViewSource. The problem occurs when more than one control shares the same view of a collection such as when a collection is bound in one case to a DataGrid and in another to the ComboBox. If the DataGrid allows the user to add items (i.e., the DataGrid's CanUserAddRows is true), the NewItemPlaceholder may have been added to the view. Try something like
<UserControl >
<UserControl.Resources >
<CollectionViewSource Source="{Binding MyCollection}"
x:Key="SourceWithoutNewItemPlaceholder" />
</UserControl.Resources>
<Grid Name="LayoutGrid" >
<ComboBox ItemsSource={Binding Source={StaticResource SourceWithoutNewItemPlaceholder}} >
</Grid>
</UserControl>
After several failed attempts i found 2 solutions:
1) In the Loaded event of the page i make a binding in the code behind, not to the DataTable itself, but to a DataTable.ToList. If i do it that way the NewItemPlaceholder won't show up.
2) In the view model i make a new property which returns the DataTable.ToList and bind to it. This way i can do the binding in XAML.
Just for reference, methods that don't work: Filter property on the ComboBox throws a NotSupportedException, seems the DataTable doesn't support this. Deleting the NewItemPlaceholder in the Loaded event of the ComboBox doesn't work either because you can't delete items when an ItemsSource is set. Removing the NewPlaceHolderItem when leaving the page with the data grid doesn't work either, because i can't find where it is (it's not in the DataTable or the View of the DataTable)
Use a CollectionViewSource to bind one control(Combobox) and collection property defined in ViewModel to bind another control (Datagrid).
Property in ViewModel :
private List<Rate> _rate = new List<Rate>();
public List<Rate> RatePlans
{
get { return _rate; }
set
{
_rate = value;
OnPropertyChanged("RatePlans");
}
}
Then in XAML :
<UserControl >
<UserControl.Resources >
<CollectionViewSource Source="{Binding RatePlans}" x:Key="RatesSource" />
</UserControl.Resources>
<Grid Name="LayoutGrid">
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<ComboBox Grid.Row="0" DisplayMemberPath="RatePlanName" ItemsSource="{Binding Source={StaticResource RatesSource}}" HorizontalAlignment="Stretch"/>
<DataGrid Grid.Row="1" HorizontalAlignment="Stretch" CanUserAddRows="True" AutoGenerateColumns="False" ItemsSource="{Binding RatePlans}">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding RatePlanName}" Header="Rate Plan" />
<DataGridTextColumn Binding="{Binding RoomType}" Header="Room Type" />
<DataGridTextColumn Binding="{Binding Price}" Header="Price"/>
</DataGrid.Columns>
</DataGrid>
</Grid>
</UserControl>
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 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}