使用 WPF 将 ObservableCollection.Count 绑定到标签
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Binding an ObservableCollection.Count to Label with WPF
提问by Pascal
I have a simple Labelthat should include the bound .Countvalue of a Property of an ObservableCollection.
我有一个简单的Label，应该包括.Count一个属性的绑定值ObservableCollection。
The thing is, that the result is always 0 (zero). The same Property is bound to a DataGrid, which works perfectly and even updates if something has changed in the Collection.
问题是，结果始终为 0（零）。相同的属性绑定到 DataGrid，它可以完美运行，甚至在集合中发生变化时也会更新。
What am I doing wrong here?
我在这里做错了什么？
Here is my code:
这是我的代码：
<Label ContentStringFormat="Members: {0}">
<Label.Content>
<Binding Path="MembersList.Count" Mode="OneWay" UpdateSourceTrigger="Default" />
</Label.Content>
</Label>
The Property looks like:
该属性看起来像：
public static ObservableCollection<Mitglied> MembersList { get; set; }
采纳答案by Vishal
You can try This...
你可以试试这个...
MainWindow.Xaml.cs->
MainWindow.Xaml.cs->
int Counter = 0;
private static ObservableCollection<string> _MemberList = new ObservableCollection<string>();
// Suppose it is of String type..I took it as of String type to check my case
public static ObservableCollection<string> MemberList
{
get { return MainWindow._MemberList; }
set { MainWindow._MemberList = value; }
}
MainWindow()
{
InitializeComponent();
MemberList.Add("0");
MemberList.Add("1");
MemberList.Add("2");
Label1.DataContext = this;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
try
{
MemberList.RemoveAt(Counter);
Counter++;
}
catch(Exception ex)
{
string strTemp=ex.Message();
}
}
MainWindow.xaml->
MainWindow.xaml->
<Grid>
<Label Name="Label1" ContentStringFormat="Members: {0}" Margin="0,56,141,38" RenderTransformOrigin="0.158,1.154" HorizontalAlignment="Right" Width="183">
<Label.Content>
<Binding Path="MemberList.Count" Mode="OneWay" UpdateSourceTrigger="Default"/>
</Label.Content>
</Label>
<Button Click="Button_Click" Width="100" Height="20" Content="click" Margin="43,169,360,122" />
</Grid>
回答by Kent Boogaart
I can only assume you've not actually added any items to the collection. If you think you are, you'll have to give us a more complete repro.
我只能假设您实际上并未向集合中添加任何项目。如果你认为你是，你必须给我们一个更完整的再现。
This works perfectly for me:
这对我来说非常有效：
MainWindow.xaml
主窗口.xaml
<Window x:Class="SO18124125.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<Button x:Name="addButton">Add</Button>
<Label>
<Label.Content>
<Binding Path="Items.Count" Mode="OneWay" UpdateSourceTrigger="Default"/>
</Label.Content>
</Label>
</StackPanel>
</Window>
MainWindow.xaml.cs
主窗口.xaml.cs
namespace SO18124125
{
using System.Collections.ObjectModel;
using System.Windows;
public partial class MainWindow : Window
{
private static readonly ObservableCollection<string> items = new ObservableCollection<string>();
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
this.addButton.Click += delegate
{
items.Add("foo");
};
}
public static ObservableCollection<string> Items
{
get { return items; }
}
}
}
BTW, this is far more succinct:
顺便说一句，这更简洁：
<Label Content="{Binding Items.Count}" ContentStringFormat="Members: {0}"/>
回答by yo chauhan
Hi You will have to Notify on CollectionChanged then it will Work
嗨，您必须通知 CollectionChanged，然后它才能工作
public class ViewModel: INotifyPropertyChanged
{
public ObservableCollection<string> MembersList { get; set; }
public ViewModel()
{
MembersList = new ObservableCollection<string>();
MembersList.CollectionChanged += collection_CollectionChanged;
MembersList.Add("wfwef");
}
void collection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
Notify("MembersList.Count");
}
private void Notify(string propName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
DataGrid uses this collectionChanged and hence working for DataGrid.
DataGrid 使用此 collectionChanged，因此适用于 DataGrid。
