C# 值更改时，WPF组合框不会更新

我有一个带有组合框和按钮的WPF应用程序。在我将值输入textbox并按下按钮后，textbox中的值应该出现在combobox的更新列表中。我正试图通过MVVM和绑定到combobox来实现这一点。下面是来自ViewModel的部分代码

public class ViewModel:INotifyPropertyChanged
    {

        DomainLogic dl = new DomainLogic();

        public event PropertyChangedEventHandler PropertyChanged;

        private ObservableCollection<string> expenseCategories = new ObservableCollection<string>();

        public ObservableCollection<string> ExpenseCategories
        {
            get
            {
                return expenseCategories;
            }
            set
            {
                expenseCategories = value;
                OnPropertyChanged("ExpenseCategories");
            }
        }

        public ViewModel()
        {
            expenseCategories = new ObservableCollection<string>(dl.GetExpenseCategories());
        }

        private void OnPropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }

以下是XAML：

<ComboBox x:Name="ExpCategory" HorizontalAlignment="Left" Margin="72,50,0,0" VerticalAlignment="Top" Width="130" ItemsSource="{Binding ExpenseCategories, UpdateSourceTrigger=PropertyChanged}" />

---

问题是，

CollectionChanged

事件不会触发

您正在DataContext中添加新元素，但没有更新数据的本地视图

更新DataContext后，应刷新您的

ObservableCollection

或使用Local

以下是如何使用

Local

：

public ViewModel()
{
      expenseCategories = dl.GetExpenseCategories().Local;
}

因此，您可以直接执行以下操作：

expenseCategories.Add(new ExpenseCategory() {textBox.Text});
dl.GetContext().SaveChanges();

或者，您必须更新

可观察收集

：

dl.CreateNewExpenseCategory(textBox.Text);
// Update your ViewModel ObservableCollection.

但是，我认为应该使用

命令，而不是事件，这样就可以直接在ViewModel内部更新
ObservableCollection

public class ViewModel:INotifyPropertyChanged
    {

        DomainLogic dl = new DomainLogic();

        public event PropertyChangedEventHandler PropertyChanged;

        private ObservableCollection<string> expenseCategories = new ObservableCollection<string>();

        public ObservableCollection<string> ExpenseCategories
        {
            get
            {
                return expenseCategories;
            }
            set
            {
                expenseCategories = value;
                OnPropertyChanged("ExpenseCategories");
            }
        }

        public ViewModel()
        {
            expenseCategories = new ObservableCollection<string>(dl.GetExpenseCategories());
        }

        private void OnPropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }

例如：

using Prism.Commands;
//Other usings
public class ViewModel : INotifyPropertyChanged
{
// Your class methods and properties
    public DelegateCommand<string> AddNewExpenseCategory
    {
       get
       {
            return new DelegateCommand<string>(Execute_AddNewExpenseCategory);
       }
    }

    public void Execute_AddNewExpenseCategory(string param)
    {
        expenseCategories.Add(new ExpenseCategory() { param });
        dl.GetContext().SaveChanges();
    }

使用Prism.Commands；
//其他用途
公共类视图模型：INotifyPropertyChanged
{
//您的类方法和属性
public DelegateCommand addNewExpenseCegory
{
得到
{
返回新的DelegateCommand（执行_addNewExpenseContegory）；
}
}
public void Execute_addNewExpenseCography（字符串参数）
{
添加（新的ExpenseCography（）{param}）；
dl.GetContext（）.SaveChanges（）；
}
Output window中有错误吗？@RackM无错误显示是否（dl.createNewExpenseCography（textBox.Text））已生成？@Babbillumpa正在编辑中
using Prism.Commands;
//Other usings
public class ViewModel : INotifyPropertyChanged
{
// Your class methods and properties
    public DelegateCommand<string> AddNewExpenseCategory
    {
       get
       {
            return new DelegateCommand<string>(Execute_AddNewExpenseCategory);
       }
    }

    public void Execute_AddNewExpenseCategory(string param)
    {
        expenseCategories.Add(new ExpenseCategory() { param });
        dl.GetContext().SaveChanges();
    }