Question

我有一个正在研究的wpf MVVM项目，我正在使用棱镜，所以INotifyPropertyChanged = SetProperty。我的模型是ComplaintModel：

public class ComplaintModel:BindableBase, IDataErrorInfo
{
    private Person _complaintPerson;
    private List<EmployeeModel> _crewList;

    public string MyStreet { get; set; }
    public string Complaint { get; set; }
    public string Response { get; set; }
    public DateTime? DateOfResponse { get; set; }
    public DateTime EntryDate { get; set; }
    public bool? Callout { get; set; }
    public string Quad { get; set; }
    public string Tap { get; set; }
    public DateTime? Modified { get; set; }

    public Person ComplaintPerson
    {
        get { return _complaintPerson; }
        set { SetProperty(ref (_complaintPerson), value); }
    }

    public List<EmployeeModel> CrewList
    {
        get { return _crewList; }
        set { SetProperty(ref (_crewList), value); }
    }

    public int ComplaintID { get; set; }

和ViewModel中的属性：

private ComplaintModel _selectedComplaint;
public ComplaintModel SelectedComplaint
{
    get { return _selectedComplaint; }
    set { SetProperty(ref (_selectedComplaint), value); }
}

EmployeeModel是

public class EmployeeModel:BindableBase,IDataErrorInfo
{
    private string _phone;
    private string _firstName;
    private string _lastName;
    public int Id { get; set; }

    public string FirstName
    {
        get { return _firstName; }
        set { SetProperty(ref(_firstName),value); }
    }

    public string LastName
    {
        get { return _lastName; }
        set { SetProperty(ref(_lastName),value); }
    }

    public string Phone
    {
        get { return _phone; }
        set { SetProperty(ref (_phone), value); }
    }

所以我尝试添加员工：

private void AddEmployee()
{

    if (SelectedEmployee == null)
    {
        SetMessage(Messages.ChooseEmployeeMessage);
        return;
    }
    if (IsReadOnly)
    {
        SetMessage(Messages.MakeEditableMessage);
        return;
    }
    if (SelectedComplaint.CrewList == null)
    {
        SelectedComplaint.CrewList = new List<EmployeeModel>();
    }

    var myList = SelectedComplaint.CrewList;
    var employee = new EmployeeModel() {FirstName = "James", Id = 1, LastName = "Tays", Phone = "1234567"};
    myList.Add(employee);
    employee = new EmployeeModel() { FirstName = "John", Id = 2, LastName = "Doe", Phone = "1234567" };
    myList.Add(employee);
    SelectedComplaint.CrewList = myList;
    SelectedEmployee = null;
}

这会将两名员工添加到CrewList，但不会更新视图。有趣的是，当我将var myList = SelectedComplaint.CrewList更改为var myList = new List<EmployeeModel>();时，它将添加2名员工并更新视图。我也尝试了SelectedComplaint.CrewList.Add(employee)，但这并没有更新视图。

如果你看到我错过了一个区域，请告诉我。

Answer 1

尝试将CrewList类型声明为＆＃34; observablecollection＆＃34;而不是＆＃34; List＆＃34;它会在您添加每个员工时更新视图。

ObservableCollection<EmployeeModel> CrewList

Answer 2

调用Add不会被视为更改属性。这就是为什么：当你这样做时：

    var myList = SelectedComplaint.CrewList;
    var employee = new EmployeeModel() {FirstName = "James", Id = 1, LastName = "Tays", Phone = "1234567"};
    myList.Add(employee);
    employee = new EmployeeModel() { FirstName = "John", Id = 2, LastName = "Doe", Phone = "1234567" };
    myList.Add(employee);
    SelectedComplaint.CrewList = myList;

您：

1）调用CrewList的getter。这将返回参考_crewList对象

2）您Add Employee - 这会修改列表，但这并不会调用CrewList的设置者 - 因此，视图不会被通知修改列表

3）将CrewList属性设置为myList变量的值。但是，请注意我在第1点中所说的内容 - myList是对同一个对象的引用 - 这不会改变你的属性（如果在setter中没有改变对象，可能Prism没有通知视图）

我的建议是将List更改为ObservableCollection - 此课程还有一个＆＃34;事件＆＃34;名为NotifyCollectionChanged - 当您致电ObservableCollection，Add()等时，会由Remove()自动提出。这会为您通知视图。

Answer 3

您需要更改

 public List<EmployeeModel> CrewList
{
    get { return _crewList; }
    set { SetProperty(ref (_crewList), value); }
}

到

public ObservableCollection<EmployeeModel> CrewList {get;set}

这将自动调用集合上的NotifyCollectionChange事件。

This帖子包含有关列表和可观察集合之间差异的更多信息。

WPF Listview不显示列表

3 个答案: