将新项目添加到 ObservableCollection 时，UI 仅更新一次

Question

一个小时前我遇到了一个非常奇怪的错误，但无法解决。我的代码包含一个绑定到我的视图（列表视图）的 ObservableCollection。我可以在我的数据库中添加一个新项目，它也会被添加到我的 ObservableCollection 中。 UI 正在正确更新，但只是第一次。如果我添加第二个项目，它将出现在我的数据库和我的集合中，但我的 UI 不再更新。谁能检查我的代码看看是否有问题？

查看：

<ListView Name="Departments_Listview" ItemsSource="{Binding Departments, UpdateSourceTrigger=PropertyChanged}" SelectedItem="{Binding YourSelectedItem, Mode=TwoWay}" Height="346">
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Department" DisplayMemberBinding="{Binding Department}"/>
        </GridView>
    </ListView.View>
</ListView>

视图模型

using Autofac;
using Calendar.Commands;
using Calendar.Database.Entities;
using Calendar.Database.Repositories;
using Calendar.Helper_Classes;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading;
using System.Windows;

namespace Calendar.ViewModels
{
    public class DepartmentViewModel : ViewModelBase
    {
        private RelayCommand command;
        private DepartmentEntity _yourSelectedItem;
        ObservableCollection<DepartmentEntity> _Departments = new ObservableCollection<DepartmentEntity>();
        public DepartmentViewModel()
        {
        }
        public ObservableCollection<DepartmentEntity> Departments
        {
            get
            {
                var container = ContainerConfig.Configure();
                using (var scope = container.BeginLifetimeScope())
                {
                    var test = scope.Resolve<IDepartmentRepository>();
                    _Departments = test.GetAll().ToObservable();
                }
                return _Departments;
            }
            set
            {
                _Departments = value;
                NotifyPropertyChanged("Departments");
            }
        }

        private string department;

        public string Department
        {
            get { return department; }
            set
            {
                department = value;
                NotifyPropertyChanged("Department");
            }
        }
        public DepartmentEntity YourSelectedItem
        {
            get
            {
                return _yourSelectedItem;
            }
            set
            {
                if (value != null)
                {
                    Department = value.Department;
                }
                _yourSelectedItem = value;
                NotifyPropertyChanged("YourSelectedItem");
            }
        }
        private void NewDepartment()
        {
            var container = ContainerConfig.Configure();
            using (var scope = container.BeginLifetimeScope())
            {
                var NewDepartment = scope.Resolve<IDepartmentRepository>();
                DepartmentEntity newDepartment = new DepartmentEntity
                {
                    Department = "Bitte ändern"
                };
                NewDepartment.Add(newDepartment);
                int DepartmentId = NewDepartment.Count();
                _Departments.Add(
                    new DepartmentEntity()
                    {
                        Id = DepartmentId,
                        Department = "Bitte ändern"
                    });
            }
        }
    }
}

Answer 1

添加新项目后尝试添加NotifyPropertyChanged("Departments");，例如之后

 _Departments.Add(
     new DepartmentEntity()
     {
         Id = DepartmentId,
         Department = "Bitte ändern"
     });

它允许 UI 理解，Departments 属性已更新。 也可以考虑在Departmentsgetter 中去掉这段代码

var container = ContainerConfig.Configure();
using (var scope = container.BeginLifetimeScope())
{
      var test = scope.Resolve<IDepartmentRepository>();
      _Departments = test.GetAll().ToObservable();
}

因为您已经将新项目添加到 _Departments 支持字段