I want to protect some rows of a DataGrid to be protected from deletion by the user, although the property CanUserDeleteRows is set to true.
Is there a possibility to protect some rows, hopefully through a databinding or a trigger? The ItemsSource is bound to an ObservableCollection of T.
If you have a property on your bound objects that can be used to determine if the current row can be deleted , like 'IsDeleteEnabled', then you can bind the DataGrid's CanUserDeleteRows property to SelectedItem.IsDeleteEnabled.
For example,
<DataGrid Name="dataGrid1"
CanUserDeleteRows="{Binding ElementName=dataGrid1, Path=SelectedItem.IsDeleteEnabled}"
Never done this with a DataGrid. Usually, when I need to control something like this, I use a ListBox and a DataTemplate with a Grid within to give it the idea of a Grid or a ListView with a GridView in the template because they both give you more control over the interaction.
A shot in the dark, since you're binding, you could use a DataGridTemplateColumn.CellEditingTemplate and make your own Delete button/text which is visible or enabled based off logic within your binding object. Maybe something like this (I didn't test this, but it should be a direction you can head)?
<dg:DataGridTemplateColumn Header="Action">
<dg:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Text Content="Delete" />
</DataTemplate>
</dg:DataGridTemplateColumn.CellTemplate>
<dg:DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ButtonEnabled="{Binding Path=IsDeleteEnabled, Mode=OneWay}" Content="Delete" Command="{Binding Path=DeleteMe}" />
</DataTemplate>
</dg:DataGridTemplateColumn.CellEditingTemplate>
</dg:DataGridTemplateColumn>
Using this method, since the command is bound to the individual object, you would probably have to raise an event your screen's ViewModel handles to remove that row from the ObservableCollection.
Again, not sure if this is the best way, but it's my 10 minute stab at it. So if it's horrible, please don't vote me down too much.
Related
WPF, MVVM
I'm finding that if I use a CollectionViewSource with my ComboBox, when I close the window, an extra call to the SelectedValue Setter is executing, if SelectedValue is bound to a string property. If I set the ItemsSource binding directly to the VM, this call does not happen. The extra call is causing values to change in the VM, resulting in incorrect data. I have other ComboBoxes setup the same way, but they bind to integer values.
CollectionViewSource definition:
<CollectionViewSource x:Key="AllClientsSource" Source="{Binding AllClients}" >
<CollectionViewSource.SortDescriptions>
<scm:SortDescription PropertyName="ClientName" />
</CollectionViewSource.SortDescriptions>
</CollectionViewSource>
ComboBox with CollectionViewSource:
<ComboBox Grid.Column="2"
ItemsSource="{Binding Source={StaticResource AllClientsSource}}"
DisplayMemberPath="ClientName" SelectedValuePath="ClientId"
SelectedValue="{Binding Path=ClientId}"
Visibility="{Binding Path=IsEditingPlan, Converter={StaticResource BoolVisibility}}" />
ComboBox direct to VM (Forgoing sorting):
<ComboBox Grid.Column="2" ItemsSource="{Binding AllClients}"
DisplayMemberPath="ClientName" SelectedValuePath="ClientId"
SelectedValue="{Binding Path=ClientId}"
Visibility="{Binding Path=IsEditingPlan, Converter={StaticResource BoolVisibility}}" />
Can anyone tell me why there is an extra setter call using the CollectionViewSource? What's different about the string binding? Is there a way to properly work around it?
EDIT: I tried changing it up and using the SelectItem property on the ComboBox. Same result. So it seems that if the item is a scalar data type, it works as expected. If it's an object, you get an extra setter call with a null value. Again, if I remove the CollectionViewSource from the equation, it works as expected.
EDIT, AGAIN: I added a link to a sample project that illustrates the issue. Targets .Net 4.5.
Run the project.
Click to display View One
Select a Client and the client's name will display on the right.
Click to display View Two
Go back to View One - Note that the selected client is no longer selected.
Click to display View Three
Select a Region and the region's name is displayed on the right.
Go back to View Two
Go back to View Three - Note that the selected region is still selected.
The only difference between the views is that One and Two use a CollectionViewSource. Three binds directly to the ViewModel. When you move to a new tab from One or Two, the setter for the selected item is getting called with a null value. Why? What's the best work-around?
Thanks.
Apparently this is caused when the CollectionViewSource is removed from the visual tree... I moved the CollectionViewSource to the ViewModel and exposed it as a property and the issue is effectively worked-around.
I have a workable solution but I'm pretty convinced there's a better way of writing this.
I have a User Control with a Data Grid inside. The Data Grid's ItemsSource is set to {Binding Path=MyView} where MyView is an ICollectionView property of the View Model. The User Control's data context is set to the View Model.
In the data grid, I have a check box header. I want to bind the IsChecked state of the checkbox to a property in the View Model.
This is what I have so far and it seems to work, but I'm concerned this binding is unnecessarily complex. The UI is pretty basic so I would expect the binding to be more straightforward to write than it was.
Is there a better way to express such a binding?
<DataGridTemplateColumn.HeaderTemplate>
<DataTemplate>
<CheckBox IsChecked="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Views:MyUserControlClass}}, Path=DataContext.AllRowsSelected}" />
</DataTemplate>
</DataGridTemplateColumn.HeaderTemplate>
In such situations I use
ElementName=userControl
instead of
RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Views:MyUserControlClass}}
Also you can use
{Binding Parent.DataContext.AllRowsSelected, ElementName=LayoutRoot}
In this case I assume that LayoutRoot is the name of the element who's parent is the user control. Parent is its property. So binding is set to parent's DataContext property.
I prefer the last variant, because providing name for user control limits its usage.
EDIT
About LayoutRoot. This name is often provided for the top element in a Window or a UserControl, or just some layout:
<Window ...>
<Grid Name="LayoutRoot">
...
</Grid>
</Window>
There's nothing special about this name. Just often used. Same situation as with namespace aliases in xaml: sys (points to mscorlib), local (points to your application namespace), etc.
I have the following Xaml (Silverlight, but it shouldn't matter):
<ListBox x:Name="Results"> ... </ListBox>
<StackPanel DataContext="{Binding ElementName=Results, Path='SelectedItem.Attributes'}">
<TextBlock Text="{Binding ElementName=Results, Path='SelectedItem.Attributes[ID]'}" />
<TextBlock Text="{Binding '[ID]'}" />
</StackPanel>
When I populate the ListBox, the second TextBlock is populated, but the first TextBlock is not. When I select any Item from the Listbox the first TextBlock is populated, but the second doesn't change.
I'm assuming that I'm missing something to tell the StackPanel's DataContext that it needs to refresh any time I change the SelectedItem in my ListBox, but I'm at a loss on what I need to do.
Ideally, I'd like to not have to bind to the whole path for each of my TextBlocks (there are going to be a bunch of them).
Gaah... I found it. Some nitwit (you read.. me) decided that it'd be smart to override the stackpanel's datacontext when I populated the ListBox. Sorry for anyone that was working on this.
I'm using PRISM v2, CAL, SL4 and MVVM and have a delegate command on my ViewModel called CheckCommand. The ItemsControl contains a checkbox and I'm trying to get the items in ItemsControl/Checkbox to fire this command when it's checked - but it's not communication back to the viewmodel!
I think it's because each items 'datacontext' is the individual object the item is bound to, rather than the ViewModel?
- My suspicion is actually correct, cause if I move my DelegateCommand out of the viewmodel and into the class defining the items in itemscontrol I can see the commands/methods beeing fired!
View:
<ListBox x:Name="BasketListBox" ItemsSource="{Binding BasketCollection}" MinWidth="200">
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox commands:Checked.Command="{Binding CheckCommand}" IsChecked="False" </CheckBox>
</DataTemplate>
</ListBox.ItemTemplate>
Can anyone point me in the right direction please?
Cheers, Mcad.
EDIT 1:
The commanding now works, see solution below. BUT, I now run into another problem:
"An exception occurred while creating a region with name 'basketRegion'. The exception was: System.InvalidOperationException: ItemsControl's ItemsSource property is not empty. This control is being associated with a region, but the control is already bound to something else. If you did not explicitly set the control's ItemSource property, this exception may be caused by a change in the value of the inherited RegionManager attached property"
Created seperate question for this problem to make it more clean:
PRISM-MVVM, ItemsControl problem with View injection
You want every CheckBox to fire the same command? You could:
<CheckBox commands:Checked.Command="{Binding DataContext.CheckCommand, ElementName=BasketListBox}"
Or you could have every child view model expose the command via their own property.
Thanx Kent. You put me on the right path to solve this, ended up doing this:
<ListBox x:Name="basketListBox" ItemsSource="{Binding basketcollection}" MinWidth="200">
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox commands:Checked1.Command="{Binding DataContext.CheckCommand, ElementName=basketListBox}" Content="{Binding basketName}"> </CheckBox>
</DataTemplate>
</ListBox.ItemTemplate>
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}