修改ItemsSource ObservableCollection后，如何刷新一个组合框 [英] How can I refresh a combobox after modifying its ItemsSource ObservableCollection

问题描述

问题很简单：当 ItemsSource 更新时，组合框不会刷新新项目似乎没有被添加到组合框中的项目列表中。

The problems is simple: when ItemsSource is updated Combobox doesn't "refresh" e.g. new items don't appear to be added to the list of items in the combobox.

我已经尝试过这个问题的答案： WPF - 自动刷新组合框内容，没有运气。

I've tried the solution from aceepted answer to this question: WPF - Auto refresh combobox content with no luck.

这里是我的代码，
XAML：

here's my code, XAML:

<ComboBox Name="LeadTypeComboBox" ItemsSource="{Binding LeadTypeCollection}" />

ViewModel：

ViewModel:

public ObservableCollection<XmlNode> LeadTypeCollection { get; set; }

我更新此集合的方式是单独的方法，它从更新的XML文件中加载数据： this.LeadTypeCollection = GetLeadTypesDataSource（）;

the way I update this collection is in the separate method, which loads data from updated XML file: this.LeadTypeCollection = GetLeadTypesDataSource();

我还尝试使用添加用于测试目的：

I've also tried using Add for testing purposes:

this.LeadTypeCollection = GetLeadTypesDataSource();
ItemToAdd = LeadTypeCollection[LeadTypeCollection.Count - 1];
this.LeadTypeCollection.Add(ItemToAdd);

代码更新集合肯定启动，调试时我可以看到这个集合中的新项目，但是在组合框中看不到它们。

the code updating collection definitely kicks off, I can see new items in this collection when debugging, but I don't see them in the combobox.

在xaml代码隐藏中执行此操作： LeadTypeComboBox.ItemsSource = MyViewModel.GetLeadTypesDataSource（）; 但是我想使用MVVM实现这一点，即代码必须在ViewModel中，不知道LeadTypeComboBox控件。

Doing this in the xaml code-behind works: LeadTypeComboBox.ItemsSource = MyViewModel.GetLeadTypesDataSource(); but I'd like to achieve this with MVVM, i.e. the code must be in ViewModel which isn't aware of LeadTypeComboBox control.

推荐答案

我想我以前看过这个，解决方案是更新收集属性来提高变化。

I think I have seen this before and the solution was to update the collection property to raise the change.

ie

public class MyViewModel : INotifyPropertyChanged
{
    private ObservableCollection<XmlNode> leadTypeCollection;

    public string LeadTypeCollection
    { 
        get { return leadTypeCollection; }
        set
        {
            if (value != leadTypeCollection)
            {
                leadTypeCollection = value;
                NotifyPropertyChanged("LeadTypeCollection");
            }
        }

    public MyViewModel()
    {
        leadTypeCollection = new ObservableCollection<XmlNode>();
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String info)
    {
        PropertyChanged.Raise(this, info);
    }
}

我有一个扩展方法来提高属性（如public static void Raise（此PropertyChangedEventHandler处理程序，对象发件人，字符串属性名称）
{b

I have an extension method for raising the property (as found elsewhere on stackoverflow):

public static void Raise(this PropertyChangedEventHandler handler, object sender, string propertyName)
{
    if (null != handler)
    {
        handler(sender, new PropertyChangedEventArgs(propertyName));
    }
}

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