[英]How to bind a list count to a label in WinForms?
How can I bind the count of a list to a label. 如何将列表的计数绑定到标签。 The following code does't get updated with the list is changed:
更改列表后,以下代码无法更新:
private IList<string> list = new List<string>();
//...
label1.DataBindings.Add("Text", list.Count, "");
Bindings listen to the PropertyChanged event of the IPropertyChanged interface. 绑定侦听IPropertyChanged接口的PropertyChanged事件。 I don't think that List.Count is reported as a PropertyChanged event when it is changed.
我不认为List.Count在更改时被报告为PropertyChanged事件。
What you could do is to implement your custom List or to find a collection that notifies when the Count is changed. 您可以做的是实现自定义列表或查找通知何时更改计数的集合。
According to Marc Gravell for this problem, he has suggested to create a facade that wraps the collection you want to bind to label1.Text 根据Marc Gravell的这个问题,他建议创建一个外观来包装你要绑定到label1.Text的集合
I have tried to implement one (for fun) and was able to get binding to Count working. 我试图实现一个(为了好玩)并且能够绑定到Count工作。
is a facade that wraps a collection to bind to. CountList<T>
是一个包装要绑定到的集合的外观。 CountList<T>
Here is the full of the demo. 这是完整的演示。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
namespace TextBindingTest
{
public partial class Form1 : Form
{
private readonly CountList<string> _List =
new CountList<string>(new List<string> { "a", "b", "c" });
public Form1()
{
InitializeComponent();
BindAll();
}
private void BindAll()
{
var binding = new Binding("Text", _List, "Count", true);
binding.Format += (sender, e) => e.Value = string.Format("{0} items", e.Value);
label1.DataBindings.Add(binding);
}
private void addToList_Click(object sender, EventArgs e)
{
_List.Add("a");
}
private void closeButton_Click(object sender, EventArgs e)
{
Close();
}
}
public class CountList<T> : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
private void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = PropertyChanged;
handler(this, e);
}
private ICollection<T> List { get; set; }
public int Count { get { return List.Count; } }
public CountList(ICollection<T> list)
{
List = list;
}
public void Add(T item)
{
List.Add(item);
OnPropertyChanged(new PropertyChangedEventArgs("Count"));
}
}
}
You can use DataSourceChanged if you have a datasource for the listbox. 如果您有列表框的数据源,则可以使用DataSourceChanged。 Just remember to update and rebind the datasource.
只需记住更新并重新绑定数据源。
This may be a bit ghetto but here is the example I worked with: 这可能有点贫民窟,但这是我合作的例子:
List<int> collection = new List<int>();
public Form1()
{
InitializeComponent();
listBox1.DataSourceChanged += listbox1_Changed;
}
private void button1_Click(object sender, EventArgs e)
{
collection.Add(new Random().Next(100));
listBox1.BeginUpdate();
listBox1.DataSource = null;
listBox1.DataSource = collection;
listBox1.EndUpdate();
}
private void listbox1_Changed(object sender, EventArgs e)
{
textBox1.Text = collection.Count.ToString();
}
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