I have created a list with ScrollViewer and stackpanel. I am adding user control to this stackpanel from codebehind.
I want to virtualize data that I can improve the performance of my application.
How can i achieve this?
I cann't use Listbox because I am adding user control as DataItems and each user control have a different width and height.. Please suggest how to implement that
Code:
XAML
<ScrollViewer>
<StackPanel x:Name="stckPnlComponentsLst" Visibility="{Binding IsBusy, Converter={StaticResource BooleanToVisibilityInvertedConverter}}" Orientation="Vertical">
</StackPanel>
</ScrollViewer>
C#
for (int count = 0; count < countItems; count++)
{
stckPnlComponentsLst.Children.Add(new ChannelNewsLstControl(ViewModel.ComponentData[count], false, false));
}
I don't see any case in which using a StackPanel inside a ScrollViewer is a good idea.
You should not do that.
There are 2 controls to do what you want, ListBox and ListView.
If you really want to stick with a stackpanel inside a ScrollViewer, just replace your StackPanel, by a VirtualizingStackPanel. But again, you should NOT be doing that.
Use a ListBox instead. Check the sample here. For example, define ListBox in a xaml
<ListBox x:Name="MyList">
and then in codebehind
var MyListData = new List<ChannelNewsLstControl>();
MyListData.Add(new ChannelNewsLstControl {name = "MyFirstChannelName});
MyList.ItemsSource=MyListData;
If you have really lots of items, i'd recommend to use Telerik's DataBoundListBox as it is much faster than a normal ListBox (at least, for wp7) and supports virtualization and async loading. Sample would be pretty the same, as component is inherited ListBox and adding own features mentioned before.
EDIT: final answer:
Try to put a grid inside of your ItemTemplate and set its RowDefinition.Height = "Auto". See some details here
Related
I have a requirement which is to display a user information at top of the page and a ListView of images will follow it, and I've wrote following code (it's a pseudocode but I think it's enough to explain what I've done):
<ScrollViewer>
<StackPanel>
<Grid>
<!-- User Information Part -->
</Grid>
<ListView>
<!-- Images Part, This is a custom virtualized ListView, it's ItemsPanel is a custom VirtualizingWrapPanel -->
</ListView>
</StackPanel>
</ScrollViewer>
But in this scenario, the VirtualizingWrapPanel (by which has been tested on another individual ListView without an explicit ScrollViewer declaration and it works correctly) and the virtualization of ListView won't work because the desired height of ScrollViewer is positive infinity and all the items in the ListView will be expanded and rendered, I wonder whether there is a way that can make the ListView in ScrollViewer being virtualizable? Thanks
You can't virtualize a list that has all elements being rendered (because of the StackPanel),
A workaround that will work for you: you need a single ListView. With the first row customized to display the User Information Part, and all other rows displaying images.
How Can I add child items to StackPanel in UserControl from C# code? Should I create something like DependencyProperty for it?
As it is easy to set Properties like Text for TextBlock in my UserControl, I have no idea how can I add items to StackPanel when using CodeBehind to do it dynamicaly.
StackPanel are only meant to be used for the most basic layout situations. It is far better using some kind of ListBox or ItemsControl depending on your requirements. You could add a collection DependencyProperty to your UserControl and do something like this:
In UserControl:
<ItemsControl ItemsSource="{Binding YourCollectionDependencyProperty, RelativeSource={
RelativeSource AncestorType={x:Type YourPrefix:YourUserControl}}}" ... />
Then you could data bind another collection property to the UserControl from outside the control:
Outside UserControl:
<YourPrefix:YourUserControl YourCollectionDependencyProperty="{Binding Items}" ... />
Then adding new items to be displayed in the UserControl is as simple as adding items to the Items collection:
Items.Add(someNewObject);
Please read the Data Binding Overview page on MSDN for further information on data binding.
Yes you can do something like this (this is just a sample):
TextBlock printTextBlock = new TextBlock();
printTextBlock.Text = "Hello, World!";
//MainStackPanel below is the name given to your control in xaml
MainStackPanel.Children.Add(printTextBlock);
Sources:
Programatically Adding Items to StackPanel
I'm using a telerik RadGridView which is pretty much the same thing as a normal DataGrid in WPF. In my gridview.columns I have a GridViewDataColumn which then allows me to put a celltemplate then a datatemplate and then allow me to put different controls within a grid. I have a combobox and a textbox(only one shows at a time based on visibility property). The problem I'm having is the tab system is kind of weird and doesn't work right. When I tab to a cell in the column above, my combobox nor my textbox ever gets focus. In fact the cell turns completly white. So I was wondering how (in code behind) can I detect when a user tabs in this particular cell and manually set focus to these child elements inside this cell on the selected row?
<telerik:GridViewDataColumn x:Name="MyDataColumn" Focusable="True" GotFocus="MyDataColumn_GotFocus_1" Header="Header1" Width="250">
<telerik:GridViewColumn.CellTemplate>
<DataTemplate>
<Grid>
<Textbox x:name="MyTextbox" Visibility="{Binding IsTextbox}"/>
<Combobox x:name="MyCombobox" Visibility="{Binding IsCombo}"/>
</Grid>
</DataTemplate>
</telerik:GridViewColumn.CellTemplate>
</telerik:GridViewDataColumn>
*Basically, how can I gain access to one of those child controls inside this GridViewDataColumn in code behind so that I can set focus to it? Thanks so much for any advice.
Probably the most straight forward answer to your question can be found by reading the answer to the Access items inside the DataTemplate in WPF post.
However, it may be worth reading the correct answer in this Access Elements inside a DataTemplate… How to for more than 1 DataTemplate? post also.
i've been banging my head on this for the last hours...
I have a User Control called "DayItem", and i want to show it 48 times in another UserControl called "DayPanel".
Let me mention this is done in MVVM style, but i'm only experiencing, and a straight way would by fine for an answer.
I have an ObservableCollection<DayItem> in the DayPanel model, and in the Xaml there's an <ItemsPresenter />.
if i do
this.ItemsSource = DayItems;
everything show up fine.
but, i wanna be able to use those DayItems in the UI like a list... to support multi-select etc.
so i tried using a ContentControl, and set it's content to the ObservableCollection.
but it just shows the ObservableCollection object's ToString text.
so i guess i need a DataTemplete there...
but why do i need a DataTemple to show a Control?
it's already styled in it's own Xaml, i don't wanna repeat it's styling again.
or maybe i'm totally wrong, anyway i need help :x
Edit:
I got this to work, saying what DataType wasn't necessary or even possible.
and in the code behind i told the listbox, that it's ItemSource was the ObservableCollection.
now i've ran into other problems... ListBox related...
There are Gaps between each control in the ListBox, which messes up the layout
and also i need to figure out a way to select multiple items by dragging...
thanks for the help so fat
First, you need a view model for you DayItem user control. Lets call it DayItemViewModel. Also I suppose you DayPanel also has a view model called something like DayPanelViewModel. Then, you DayPanelViewModel would expose a collection of DayItemViewModel instances:
public class DayPanelViewModel
{
public ObservableCollection<DayItemViewModel> DayItems { get; set; }
}
Then, in your DayPanel.xaml:
<UserControl x:Class="DayPanel"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<UserControl.Resources>
<DataTemplate x:Key="DayItemTemplate"
DataType="{x:Type my:DayItemViewModel}">
<my:DayItem />
</DataTemplate>
</UserControl.Resources>
<Grid>
<ListBox ItemsSource="{Binding DayItems}"
ItemTemplate="{StaticResource DayItemTemplate}" />
</Grid>
</UserControl>
Try using ListBox, since that implements multiselect...
Also it might be wise (for MVVM) if you do not contain DayItems, but DayItemModel's in your DayPanelModel, and set the ListBox's ItemTemplate to present each DayItemModel with a DayItem.
How would I create a control like the example at this site as a User Control?
So, instead of doing this:
<ScrollViewer>
<StackPanel>
<!– Content –>
</StackPanel>
</ScrollViewer>
I could do this:
<ScrollableStackPanel>
<!– Content –>
</ScrollableStackPanel>
Unfortunately, there is no way to do that as a UserControl in WPF. You would need to make a custom control (instead of a user control) based on ItemsControl. It could handle this correctly.
That being said, I don't see much point in this. It's very easy to just put your StackPanel within a ScrollViewer - why reinvent the wheel?
It looks like you just need to use a ListBox. You can override the ItemContainterStyle and ListBox.Style to get rid of all the Selected behaviours and backgrounds if you want. Because a ListBox has StackPanel and ScrollViewer in it by default.