我是WPF和MVVM的初学者。在对其进行编码时，我遇到了VehicleAddViewModel类中的ListItems变量的问题，该类的类型为ObservableCollection List。 从View到ViewModel的绑定是正确的，ListItems正在更新，Even OnPropertyChanged方法也在工作，但是当我向ListItems添加新的List时，它没有反映到UI。
另一方面，如果我将ListItems对象设为静态，它就会开始工作。 我不知道为什么会这样。
我很想知道为什么会这样。
我有大量文件，所以只为我的工作和非工作版本提供相关文件，如果您需要任何其他文件，请告诉我。
ListOfVehicle.xaml
<Window x:Class="Seris.ListOfVehicle"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="ListOfVehcle" Height="600" Width="700"
xmlns:l="clr-namespace:Seris.ViewModels"
xmlns:cnv="clr-namespace:Seris.Converters">
<Window.Resources>
<cnv:ID2Name x:Key="converter" />
</Window.Resources>
<Grid HorizontalAlignment="Center">
<Label Content="Manage Vehicle" HorizontalAlignment="Left" Height="27" Margin="261,8,0,0" VerticalAlignment="Top" Width="103" FontWeight="Bold" FontSize="12"/>
<Label Content="SERIS CAD" HorizontalAlignment="Left" Height="30" Margin="53,8,0,0" VerticalAlignment="Top" Width="84" FontWeight="Bold"/>
<Menu x:Name="ListOfPersonnnel" HorizontalAlignment="Left" Height="32" Margin="10,35,0,0" VerticalAlignment="Top" Width="603">
<MenuItem Header="Manage Vehicle >>" />
</Menu>
<Button Name="Add_Button" CommandParameter="add" Command="{Binding OpenAddWindow_Command}" Content="Add" Height="28" Width="81" Margin="246,396,315,46"/>
<Button Name="Replace_Button" CommandParameter="replace" Command="{Binding ReplaceButton_Command}" IsEnabled="{Binding IsEnableReplaceButton, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Content="Replace" Height="28" Width="81" Margin="345,396,216,46"/>
<Button Name="Remove_Button" CommandParameter="remove" Command="{Binding RemoveButton_Command}" IsEnabled="{Binding IsEnableReplaceButton, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Content="Remove" Height="28" Width="81" Margin="442,396,119,46"/>
<ListView Name ="Grid" Margin="104,67,185,226" >
<DataGrid Name="DG" ItemsSource="{Binding ListItems, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedItem="{Binding SelectedRow, Mode=TwoWay}" SelectionMode="Single" GridLinesVisibility="None" IsReadOnly="True" AutoGenerateColumns="False" BorderThickness="0">
<DataGrid.DataContext>
<l:VehicleAddViewModel />
</DataGrid.DataContext>
<DataGrid.Columns>
<DataGridTextColumn Header="Vehicle No" Binding="{Binding VehicleNo}"/>
<DataGridTextColumn Header="Model" Binding="{Binding Model}" />
<DataGridTextColumn Header="ManufacturingDate" Binding="{Binding ManufacturingDate}" />
<DataGridTextColumn Header="IUNo" Binding="{Binding IUNo}" />
<DataGridTextColumn Header="Personnel" Binding="{Binding PersonnelNameSelected, Converter={StaticResource converter} }" />
<DataGridTextColumn Header="Unique No" Binding="{Binding UniqueNo}"/>
</DataGrid.Columns>
</DataGrid>
</ListView>
<TextBox Name="Search_Text" Text="{Binding SearchString, Mode=OneWayToSource, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Height="23" Margin="520,72,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120" />
</Grid>
</Window>
ListOfVehicle.xaml.cs
using Seris.ViewModels;
using Seris.Views;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace Seris
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class ListOfVehicle : Window
{
public ListOfVehicle()
{
this.DataContext = VehicleMainViewModel.getInstance;
this.Show();
InitializeComponent();
}
}
}
ObservableObject.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Windows;
namespace Seris.Models
{
public abstract class ObservableObject: INotifyPropertyChanged, IDisposable
{
public event PropertyChangedEventHandler PropertyChanged;
protected bool OnPropertyChanged(string propertyName)
{
this.VerifyPropertyName(propertyName);
PropertyChangedEventHandler handler = PropertyChanged;
if(handler!=null)
{
if (propertyName != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
return true;
}
}
return false;
}
public void VerifyPropertyName(string propertyName)
{
if (TypeDescriptor.GetProperties(this)[propertyName] == null)
{
string msg = "Invalid Property Name: " + propertyName;
if (this.ThrowOnInvalidPropertyName)
throw new Exception(msg);
else
Debug.Fail(msg);
}
}
public virtual void Dispose()
{
// To Override this method
}
public bool ThrowOnInvalidPropertyName { get; set; }
}
}
VehicleAddViewModel.cs
...
private ObservableCollection<VehicleModel> _listItems = new ObservableCollection<VehicleModel>();
public ObservableCollection<VehicleModel> ListItems
{
get { return _listItems; }
set
{
if (value == null || (!value.Equals(_listItems)))
{
_listItems = value;
OnPropertyChanged("ListItems");
}
}
}
...
public void SaveToList(object o1)
{
try
{
// Setting Flags
ErrorMessage = "";
//Checking a duplicate entry
if (isDuplicate())
{
throw (new Exception("Duplicate Entries are not allowed"));
}
// Adding a Record
using(vm = new VehicleModel(true,VehicleNo, Model, ManufacturingDate, IUNo, PersonnelNameSelected))
{
// Keeping record of selected Row
int indexToRemove;
if (SelectedRow != null && ReplaceFlag==true)
{
ReplaceFlag = false;
VehicleModel selectedRecord = ListItems.First(x => x.UniqueNo == UniqueNo);
indexToRemove = ListItems.IndexOf(selectedRecord);
ListItems.Insert(indexToRemove, new VehicleModel(vm));
ListItems.RemoveAt(indexToRemove + 1);
}
else
ListItems.Add(new VehicleModel(vm));
}
VehicleMainViewModel.getInstance.CloseAdd();
// Clearing Form
clearAllData();
}
catch (Exception ex)
{
ErrorMessage = ex.Message;
}
}
...
public VehicleAddViewModel()
{
// Setting Flags
ErrorMessage = "";
IsEnableReplaceButton = false;
// Commands Initialization
try
{
SaveButton_Command = new RelayCommand(new Action<object>(SaveToList));
}
catch(Exception ex)
{
showMessage("Exception Occured in Command Variables");
}
}
#endregion
}
}
VehicleMainViewModel
{
public class VehicleMainViewModel: ObservableObject
{
...
public VehicleMainViewModel()
{
//VehicleMainViewModel.ListItems = new ObservableCollection<VehicleModel>();
//VehicleMainViewModel.PersonnelObject = PersonnelMainViewModel.getInstance._Personnel_List;
try
{
ReplaceButton_Command = new RelayCommand(new Action<object>(ReplaceToList));
RemoveButton_Command = new RelayCommand(new Action<object>(RemoveList));
OpenAddWindow_Command = new RelayCommand(new Action<object>(OpenAdd));
}
catch (Exception ex)
{
VehicleAddViewModel.showMessage("Exception Occured in Command Variables");
}
}
}
}
＆＃34;现在我只更改了2个文件VehicleAddViewModel和VehicleMainViewModel，如下所示，我所做的只是使ListView对象静态，它开始工作......＆＃34; < / p>
VehicleAddViewModel
public class VehicleAddViewModel : ObservableObject
{
. . .
private static ObservableCollection<VehicleModel> _listItems = new ObservableCollection<VehicleModel>();
public static ObservableCollection<VehicleModel> ListItems
{
get { return _listItems; }
set
{
if (value == null || (!value.Equals(_listItems)))
{
_listItems = value;
}
}
}
#region Methods
private VehicleModel vm;
public void SaveToList(object o1)
{
try
{
// Setting Flags
ErrorMessage = "";
//Checking a duplicate entry
if (isDuplicate())
{
throw (new Exception("Duplicate Entries are not allowed"));
}
// Adding a Record
using(vm = new VehicleModel(true,VehicleNo, Model, ManufacturingDate, IUNo, PersonnelNameSelected))
{
// Keeping record of selected Row
int indexToRemove;
if (SelectedRow != null && ReplaceFlag==true)
{
ReplaceFlag = false;
VehicleModel selectedRecord = ListItems.First(x => x.UniqueNo == UniqueNo);
indexToRemove = ListItems.IndexOf(selectedRecord);
ListItems.Insert(indexToRemove, new VehicleModel(vm));
ListItems.RemoveAt(indexToRemove + 1);
}
else
ListItems.Add(new VehicleModel(vm));
}
VehicleMainViewModel.getInstance.CloseAdd();
// Clearing Form
clearAllData();
}
catch (Exception ex)
{
ErrorMessage = ex.Message;
}
}
public VehicleAddViewModel()
{
// Setting Flags
ErrorMessage = "";
IsEnableReplaceButton = false;
// Commands Initialization
try
{
SaveButton_Command = new RelayCommand(new Action<object>(SaveToList));
}
catch(Exception ex)
{
showMessage("Exception Occured in Command Variables");
}
}
#endregion
}
}