Web Service更新后，组合框中的“选定项目”未更改其值

Question

I have a WPF user control that contains a combo box:

<UserControl
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation" x:Class="Hartville.SalesScriptApplication.Views.SalesScriptEditorGroups" 
             mc:Ignorable="d" 
         xmlns:events="http://schemas.microsoft.com/expression/2010/interactivity"
         xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WPF4"
             xmlns:hartvm="clr-namespace:Hartville.SalesScript.ViewModels;assembly=Hartville.SalesScript.ViewModels"
             d:DesignHeight="106" d:DesignWidth="909" Background="#FFF3EDED">
    <UserControl.Resources>
        <ResourceDictionary>
            <hartvm:ViewLocator x:Key="HartvilleLocator" d:IsDataSource="True" />
        </ResourceDictionary>
    </UserControl.Resources>
    <UserControl.DataContext>
        <Binding Source="{StaticResource HartvilleLocator}" Path="ScriptEditorGroups" />
    </UserControl.DataContext>
    <Border>
        <Grid Margin="5,10,0,20">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <StackPanel Orientation="Horizontal" Margin="0,10,0,20">
                <TextBlock TextWrapping="Wrap" Text="Selected Script Group:"/>
                <ComboBox Width="250" Margin="10,0,0,0" HorizontalAlignment="Left" ItemsSource="{Binding ScriptGroups}" SelectedItem="{Binding SelectedScriptGroup}" 
                    DisplayMemberPath="Name" >
                    <events:Interaction.Triggers>
                        <events:EventTrigger EventName="SelectionChanged">
                            <cmd:EventToCommand Command="{Binding ScriptGroupSelectedCommand}" PassEventArgsToCommand="False" />
                        </events:EventTrigger>
                    </events:Interaction.Triggers>              
                </ComboBox>
            </StackPanel>
    </Border>
</UserControl>

NOTE: We are using MVVM light framework. The view locator that you see is just a class that instantiates the view model which you will see referenced in the data context portion.

When something is selected from the combo box and the edit button is clicked, the user can update the name and save it. However, when the user clicks save, you can see the changed selection in the combobox but the selected item still contains the original name. So, for example, I select the option "Hello World" from the combo box. I change the name to "FOOBAR" and click save. I update the selected item in the code (and I can see that the property is changing). When I check the combo box I see "FOOBAR" but the selected value still says "Hello World". Also, "Hello World" no longer exists in the combobox (obviously because I just updated it.

Here is the code for the view model:

using System.Windows.Input;
using System.Collections.ObjectModel;
using GalaSoft.MvvmLight.Command;
using Hartville.Common.Controls.ViewModels;
using Hartville.Common.Controls.ViewModels.Validation;
using Hartville.SalesScript.ViewModels.Messages;
using Hartville.Values.Sales;
using System.Linq;

namespace Hartville.SalesScript.ViewModels.Scripts
{
    public class ScriptEditorGroups: CommonViewModelBase
    {
        private ObservableCollection<ScriptHeader> _scriptGroups;
        private ObservableCollection<Script> _scripts; 
        private ScriptHeader _selectedScriptGroup;
        private Script _selectedScript;
        private bool _isScriptGroupActive;
        private string _groupName;
        private bool _shouldEnableScriptGroup;
        private bool _shouldShowGroupEditPanel;
        private bool _shouldUseDefaultScript;
        private bool _shouldShowScriptSelection;

        public ICommand EditSelectedCommand { get; set; }
        public ICommand NewGroupCommand { get; set; }
        public ICommand SaveCommand { get; set; }
        public ICommand ScriptGroupSelectedCommand { get; set; }

        public ObservableCollection<ScriptHeader> ScriptGroups
        {
            get { return _scriptGroups; }
            set { SetPropertyValue(ref _scriptGroups, value); }
        }

        public ObservableCollection<Script> Scripts
        {
            get { return _scripts; }
            set { SetPropertyValue(ref _scripts, value); }
        }

        public ScriptHeader SelectedScriptGroup
        {
            get { return _selectedScriptGroup; }
            set { SetPropertyValue(ref _selectedScriptGroup, value ); }
        }

        public Script SelectedScript
        {
            get { return _selectedScript; }
            set { SetPropertyValue(ref _selectedScript, value); }
        }

        public bool IsScriptGroupActive
        {
            get { return _isScriptGroupActive; }
            set { SetStructPropertyValue(ref _isScriptGroupActive, value); }
        }

        public string GroupName
        {
            get { return _groupName; }
            set { SetStructPropertyValue(ref _groupName, value); }
        }

        public bool ShouldEnableScriptGroup
        {
            get { return _shouldEnableScriptGroup; }
            set { SetStructPropertyValue(ref _shouldEnableScriptGroup, value); }
        }

        public bool ShouldShowGroupEditPanel
        {
            get { return _shouldShowGroupEditPanel; }
            set { SetStructPropertyValue(ref _shouldShowGroupEditPanel, value); }
        }

        public bool ShouldUseDefaultScript
        {
            get { return _shouldUseDefaultScript; }
            set { SetStructPropertyValue(ref _shouldUseDefaultScript, value); }
        }

        public bool ShouldShowScriptSelection
        {
            get { return _shouldShowScriptSelection; }
            set { SetStructPropertyValue(ref _shouldShowScriptSelection, value); }
        }

        public bool IsEdit { get; set; }
        public bool IsNew { get; set; }

        protected override void RegisterForMessages()
        {
            MessengerService.Register<BeginSalesScriptEditorMessage>(OnBeginSalesScriptEditor);

            EditSelectedCommand = new RelayCommand(OnEdit);
            NewGroupCommand = new RelayCommand(OnNewGroup);
            SaveCommand = new RelayCommand(OnSave);
            ScriptGroupSelectedCommand = new RelayCommand(OnScriptGroupSelected);
        }

        private void OnBeginSalesScriptEditor(BeginSalesScriptEditorMessage message)
        {
            ScriptGroups = new ObservableCollection<ScriptHeader>(SalesService.GetAllScriptHeader());
            Scripts = new ObservableCollection<Script>(SalesScriptCache.Scripts);

            ShouldEnableScriptGroup = false;
            ShouldShowGroupEditPanel = false;
            ShouldShowScriptSelection = false;
            IsEdit = false;
            IsNew = false;
        }

        private void OnEdit()
        {
            if(SelectedScriptGroup == null) return;

            IsEdit = true;
            ShouldShowGroupEditPanel = true;
            ShouldShowScriptSelection = true;
            GroupName = SelectedScriptGroup.Name;
            SelectedScript = SalesScriptCache.Scripts.FirstOrDefault(s => s.ScriptId == SelectedScriptGroup.StartScriptId);
        }

        private void OnNewGroup()
        {
            IsNew = true;
            GroupName = string.Empty;
            ShouldShowGroupEditPanel = true;
            ShouldShowScriptSelection = false;
        }

        private void OnSave()
        {
            ThreadManagement.ExecuteInSeparateThread(ProcessScriptUpdate);
        }

        private void OnScriptGroupSelected()
        {
            if(SelectedScriptGroup == null) return;

            MessengerService.Send(ScriptHeaderSelectedMessage.Create(SelectedScriptGroup));
            ShouldEnableScriptGroup = true;
        }

        protected override void SetDesignTimeInfo(){}

        protected void ResetValues()
        {
            ShouldEnableScriptGroup = false;
            ShouldShowGroupEditPanel = false;
            IsScriptGroupActive = false;
            IsEdit = false;
            IsNew = false;
            ShouldShowScriptSelection = false;
        }

        private int CreateNewScriptGroup()
        {
            var scriptHeader = new ScriptHeader
                                   {
                                       Name = GroupName,
                                       IsActive = IsScriptGroupActive
                                   };

            MessengerService.Send(ScriptHeaderSelectedMessage.Create(scriptHeader));
            return SalesService.ScriptHeaderInsertUpdate(scriptHeader);
        }

        private int EditExistingScriptGroup()
        {
            if(SelectedScriptGroup == null) return 0;

            var scriptHeader = new ScriptHeader
                                   {
                                       Name = GroupName,
                                       IsActive = IsScriptGroupActive,
                                       ScriptHeaderId = SelectedScriptGroup.ScriptHeaderId,
                                       StartScriptId = SelectedScript.ScriptId
                                   };

            MessengerService.Send(ScriptHeaderSelectedMessage.Create(scriptHeader));
            return SalesService.ScriptHeaderInsertUpdate(scriptHeader);
        }

        private void ProcessScriptUpdate()
        {
            var returnId = 0;

            if (IsNew)
                returnId = CreateNewScriptGroup();
            else if (IsEdit)
                returnId = EditExistingScriptGroup();

            ScriptGroups = new ObservableCollection<ScriptHeader>(SalesService.GetAllScriptHeader());
            SelectedScriptGroup = ScriptGroups.FirstOrDefault(h => h.ScriptHeaderId == returnId);

            ResetValues();
        }
    }
}

How do I fix this issue?

EDIT:

This is the SetPropertyValue method that calls the notify:

public virtual void SetPropertyValue<T>(ref T currentValue, T newValue, Action<T> extraFunction = null, Action voidAfterSetAction = null) where T : class
        {
            if (currentValue == newValue) return;

            currentValue = newValue;

            PropertyHasChanged();

            if (extraFunction != null) extraFunction(newValue);

            if (voidAfterSetAction != null) voidAfterSetAction();
        }

EDIT:

This is the entire base class that holds the property change code:

using System;
using System.ComponentModel;
using System.Diagnostics;
using GalaSoft.MvvmLight;
using Hartville.Common.Controls.Messaging;
using Hartville.Common.Controls.Modules;
using Hartville.Common.Controls.ViewModels.Validation;
using Hartville.Common.Controls.WebServices;
using Hartville.Common.Threading;

namespace Hartville.Common.Controls.ViewModels
{
    public abstract class CommonViewModelBase : ViewModelBase, IDataErrorInfo
    {


        public string this[string columnName]
        {
            get
            {
                var validationReturn = ValidationManager.Validate(columnName);

                OnValidationComplete();

                return validationReturn;
            }
        }

        public string Error
        {
            get { return null; }
        }

        protected CommonViewModelBase()
        {
            ValidationManager = ValidationManager.Start(this);

            RegisterForMessages();

            if (IsInDesignMode) SetDesignTimeInfo();
        }

        public virtual void Reset()
        {
            IsProcessing = false;
        }

        public virtual void OnValidationComplete()
        {
        }

        public virtual void SetPropertyValue<T>(ref T currentValue, T newValue, Action<T> extraFunction = null, Action voidAfterSetAction = null) where T : class
        {
            if (currentValue == newValue) return;

            currentValue = newValue;

            PropertyHasChanged();

            if (extraFunction != null) extraFunction(newValue);

            if (voidAfterSetAction != null) voidAfterSetAction();
        }

        public virtual void SetPropertyValue<T>(ref T currentValue, T newValue, Action extraFunction) where T : class
        {
            if (currentValue == newValue) return;

            currentValue = newValue;

            PropertyHasChanged();

            if (extraFunction != null) extraFunction();
        }

        public virtual void SetStructPropertyValue<T>(ref T currentValue, T newValue, Action<T> extraFunction = null, Action voidActionAfterSetAction = null)
        {
            currentValue = newValue;

            PropertyHasChanged();

            if (extraFunction != null) extraFunction(newValue);

            if (voidActionAfterSetAction != null) voidActionAfterSetAction();
        }

        public virtual void SetStructPropertyValue<T>(ref T currentValue, T newValue, Action extraFunction)
        {
            currentValue = newValue;

            PropertyHasChanged();

            if (extraFunction != null) extraFunction();
        }

        public virtual void SetValue<T>(ref T currentValue, T newValue, Action<T> voidOldValueAction = null, Action voidAfterSetAction = null) where T : class
        {
            var oldVal = currentValue;

            if (currentValue == newValue) return;

            currentValue = newValue;

            PropertyHasChanged();

            if (voidOldValueAction != null) voidOldValueAction(oldVal);

            if (voidAfterSetAction != null) voidAfterSetAction();
        }

        protected abstract void RegisterForMessages();
        protected abstract void SetDesignTimeInfo();

        protected void SendModalCloseMessage()
        {
            MessengerService.Send(ModalCommandMessage.Create(ModalOptions.Close));
        }

        protected void SendModalOpenMessage(ModalName windowName, Guid? customID = null)
        {
            MessengerService.Send(ModalCommandMessage.Create(ModalOptions.Open, windowName, customID));
        }

        private void PropertyHasChanged()
        {
            var currentFrame = 2;

            var frame = new StackFrame(currentFrame);

            var propertyName = string.Empty;

            if (frame.GetMethod().Name.Length > 4) propertyName = GetPropertyName(frame);

            while (!frame.GetMethod().Name.StartsWith("set_"))
            {
                currentFrame++;

                frame = new StackFrame(currentFrame);

                if (frame.GetMethod().Name.Length > 4) propertyName = GetPropertyName(frame);
            }

            RaisePropertyChanged(propertyName);
        }

        private static string GetPropertyName(StackFrame frame)
        {
            return frame.GetMethod().Name.Substring(4);
        }
    }
}

Answer 1

You need to implement iNotifyPropertyChanged and call PropertyChanged in

    public ScriptHeader SelectedScriptGroup 
    { 
        set { SetPropertyValue(ref _selectedScriptGroup, value ); } 
    } 

Answer 2

Adding to what Blam has already mentioned, you must implement INotifyPropertyChanged interface in your CommonViewModelBase or current view model. And you should call the PropertyChanged method for all the property setters whose values you are changing after the Datacontext has been assigned to the view.

public ScriptHeader ScriptGroups
{ 
    set { SetPropertyValue(ref _selectedScriptGroup, value ); 
          PropertyChanged("SelectedScriptGroup ");
        } 
}

public ScriptHeader SelectedScriptGroup 
{ 
    set { SetPropertyValue(ref _selectedScriptGroup, value ); 
          PropertyChanged("SelectedScriptGroup");
        } 
}

Else, there is no way for your View to know that the property value to which the control is binding has changed. For implementation, please refer to Property Changed Implementation