ASP.NET controls like ListView allows providing a custom template by setting the ListView.EmptyDataTemplate property, this template will be rendered in case of empty data source.
How to do the same in WPF (XAML only preferrable) for ItemsControl based controls like ListView and DataGrid? So I want to show my custom DataTemplate in case when ItemsSource is empty.
There is a 100% xaml solution that makes use of the "HasItems" dependancy property.
<ItemsControl>
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Description}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.Style>
<Style TargetType="ItemsControl">
<Style.Triggers>
<Trigger Property="HasItems" Value="false">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<TextBlock Text="This Control is empty"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
</ItemsControl.Style>
</ItemsControl>
You can use set the Template property based on a DataTrigger
For example,
In Resources:
<ControlTemplate x:Key="EmptyListBoxTemplate">
<TextBlock Text="Items count == 0" />
</ControlTemplate>
Control itself:
<ListBox ItemsSource="{Binding SomeCollection}">
<ListBox.Style>
<Style TargetType="{x:Type ListBox}">
<Style.Triggers>
<DataTrigger Value="{x:Null}" Binding="{Binding DataContext.SomeCollection, RelativeSource={RelativeSource Self}}">
<Setter Property="Template" Value="{StaticResource EmptyListBoxTemplate}" />
</DataTrigger>
<DataTrigger Value="0" Binding="{Binding DataContext.SomeCollection.Count, RelativeSource={RelativeSource Self}}">
<Setter Property="Template" Value="{StaticResource EmptyListBoxTemplate}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ListBox.Style>
</ListBox>
There might be an simplier way of doing the binding, but I don't have a compiler on me right now to figure out what it would be :)
DataContext.SomeCollection.Count return 0 in case when DataContext.SomeCollection is null?
SomeCollection is equal to {x:Null}ListBox.DataContext.SomeCollection.Count, which should be a valid path since ItemsSource="{Binding SomeCollection}" is a valid path. I can't remember the value that gets returned if the binding is not valid, but if SomeCollection is null then WPF will ignore the binding error caused by .Count. It won't throw an exception.you can use DataTemplate selector to do that.
http://msdn.microsoft.com/en-us/library/system.windows.controls.datatemplateselector.aspx
UPDATE 1
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace EmptyRowsTemplate
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.Loaded += (o, e) =>
{
this.l.ItemsSource = new List<string>(3)
{
"A",
null,
"B"
};
};
}
}
public class TemplateManager : DependencyObject
{
public static readonly DependencyProperty BlankDataTemplateProperty =
DependencyProperty.RegisterAttached("BlankDataTemplate",
typeof(DataTemplate),
typeof(TemplateManager),
new PropertyMetadata(new PropertyChangedCallback((o, e) =>
{
((ItemsControl)o).ItemTemplateSelector = new BlankDataTemplateSelector();
})));
public static void SetBlankDataTemplate(DependencyObject o, DataTemplate e)
{
o.SetValue(TemplateManager.BlankDataTemplateProperty, e);
}
public static DataTemplate GetBlankDataTemplate(DependencyObject o)
{
return (DataTemplate)o.GetValue(TemplateManager.BlankDataTemplateProperty);
}
private class BlankDataTemplateSelector : DataTemplateSelector
{
public BlankDataTemplateSelector()
: base()
{
}
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
ItemsControl itemControl =
(ItemsControl)ItemsControl.ItemsControlFromItemContainer(ItemsControl.ContainerFromElement(null, container));
if (item == null)
{
return TemplateManager.GetBlankDataTemplate(itemControl);
}
else
{
return base.SelectTemplate(item, container);
}
}
}
}
}
Markup
<Window x:Class="EmptyRowsTemplate.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:EmptyRowsTemplate"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ListBox x:Name="l">
<local:TemplateManager.BlankDataTemplate>
<DataTemplate>
<Button Background="Red">No Data!</Button>
</DataTemplate>
</local:TemplateManager.BlankDataTemplate>
</ListBox>
</Grid>
</Window>