Viewmodel的多个实例

时间：2011-03-21 15:40:45

标签： wpf mvvm

我是WPF和MVVM的新手（这是我在WPF中的第一个项目）。我正在处理的项目应该接受一些搜索条件，并在网格中显示结果。要构造查询我正在使用动态LINQ查询。我似乎在管理ProjectSearchViewModel的实例时遇到问题，该实例对应于负责收集搜索条件和执行查询的视图。创建MainWindowViewModel时会创建一个实例。这将创建所有其他viewmodel实例。这就是我的期望。但是当显示MainWindow的时候，我得到另一个ProjectSearchViewModel，我想从绑定。

一般的想法是：

  1. 搜索条件填入ProjectSearchView。

  2. 按下加载命令后，我使用Reactive Extensions方法发送SearchResultMessage。

  3. MainWindowViewModel

    4. 接收消息

  4. MainWindowViewModel正在查询ProjectSearchViewModel.SearchResult，并将IObservable List分配给AllProjectsViewModel.AllProjects，它绑定到数据网格以显示结果（AllProjectView负责显示带有结果项目列表的网格）

    < / LI>

    问题是SearchResultMessage的参数填充和发送发生在ProjectSearchViewModel的一个实例中，并且从MainWindowViewModel实际查询SearchResult发生在另一个实例中，其中所有搜索条件都是空的。

    我想我别无选择，只能发布我的代码：这里是它的删节版本，省略了一些iDisposable管道等等。对于我的模型，我使用Entity Framework 4。

    正如我所提到的，我是一个全新的人，所以如果有人看到任何公然无视常识的话，请指好我。 

    


    Imports Cheminator.ViewModel
    


    Partial Public Class App

    Inherits Application


    Private viewModel As MainWindowViewModel

    Private window As MainWindow

    Protected Overrides Sub OnStartup(ByVal e As StartupEventArgs)

        MyBase.OnStartup(e)

        window = New MainWindow

        viewModel = New MainWindowViewModel '1st instance of ProjectSearchViewModel created Here

        window.DataContext = viewModel

        window.Show() '2nd instance of ProjectSearchViewModel created Here

    End Sub

End Class

    



    Partial Public Class App

    Inherits Application


    Private viewModel As MainWindowViewModel

    Private window As MainWindow

    Protected Overrides Sub OnStartup(ByVal e As StartupEventArgs)

        MyBase.OnStartup(e)

        window = New MainWindow

        viewModel = New MainWindowViewModel '1st instance of ProjectSearchViewModel created Here

        window.DataContext = viewModel

        window.Show() '2nd instance of ProjectSearchViewModel created Here

    End Sub

End Class


        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Cheminator"
    xmlns:vm="clr-namespace:Cheminator.ViewModel"
    xmlns:vw="clr-namespace:Cheminator.Views"
    xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
xmlns:dxd="http://schemas.devexpress.com/winfx/2008/xaml/docking"
xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
xmlns:dxnb="http://schemas.devexpress.com/winfx/2008/xaml/navbar"
xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid"
xmlns:collections="clr-namespace:System.Collections;assembly=mscorlib"
    Title="DXWpfApplication" Height="600" Width="800"
    dx:ThemeManager.ThemeName="Office2007Blue"
>

<Window.Resources>
    <ResourceDictionary Source="MainWindowResources.xaml" />
</Window.Resources>

<dxd:DockLayoutManager>
    <dxd:LayoutGroup>
        <dxd:LayoutGroup Orientation="Vertical"  Width="3*">
            <dxd:DocumentGroup Height="3*" SelectedTabIndex="0">
                <dxd:DocumentPanel Caption="Document1" Height="3*" >
                     <ContentControl
                      Content="{Binding Path=ProjectsVM}"
                      />
                </dxd:DocumentPanel>
            </dxd:DocumentGroup>
            <dxd:LayoutPanel Caption="Search Criteria" Height="*"  CaptionImage="Images/Icons/DetailView.png">                  

                <ContentControl
                      Content="{Binding Path=ProjectsSearchVM}"
                      />
            </dxd:LayoutPanel>
        </dxd:LayoutGroup>
    </dxd:LayoutGroup>
</dxd:DockLayoutManager>


    <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Cheminator"
xmlns:vm="clr-namespace:Cheminator.ViewModel"
xmlns:vw="clr-namespace:Cheminator.Views"    >

<DataTemplate DataType="{x:Type vm:AllProjectsViewModel}">
    <vw:AllProjectsView />
</DataTemplate>

<DataTemplate DataType="{x:Type vm:ProjectSearchViewModel}">
    <vw:ProjectSearchView />
</DataTemplate>

    <UserControl x:Class="Cheminator.Views.AllProjectsView"
         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:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
         xmlns:dxd="http://schemas.devexpress.com/winfx/2008/xaml/docking"
         xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
         xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid"       
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:vm="clr-namespace:Cheminator.ViewModel"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">

    <dxg:GridControl AutoPopulateColumns="True" ShowBorder="False" >
        <dxg:GridControl.DataSource>
            <Binding Path="AllProjects"/>                     
        </dxg:GridControl.DataSource>
        <dxg:GridControl.View>
            <dxg:TableView>

        </dxg:TableView>
        </dxg:GridControl.View>
   </dxg:GridControl>
</UserControl>

    <UserControl x:Class="Cheminator.Views.ProjectSearchView"
         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:vm="clr-namespace:Cheminator.ViewModel"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="160" d:DesignWidth="470">
<Grid Height="160" Width="470">
    <Grid.DataContext>
        <vm:ProjectSearchViewModel />
    </Grid.DataContext>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="175*" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <Label Content="Cotation ID:" Height="28" Margin="49,12,32,0" Name="Label1" VerticalAlignment="Top" />
    <TextBox Grid.Column="1" Height="23" Margin="0,14,159,0" Name="CotationIDTextBox" VerticalAlignment="Top" Text="{Binding Path=CotationID, UpdateSourceTrigger=LostFocus}"/>

    <Label Grid.Row="1" Content="Cotation Name:" Height="28" Margin="49,6,6,0" Name="Label2" VerticalAlignment="Top" />
    <TextBox Grid.Row="1" Grid.Column="1" Height="23" Margin="0,8,159,0" Name="CotationNameTextBox" VerticalAlignment="Top" Text="{Binding Path=ProjectSummary, UpdateSourceTrigger=PropertyChanged}"/>

        <Label Grid.Row="2" Content="User:" Height="28" Margin="49,6,32,0" Name="Label3" VerticalAlignment="Top" />
    <TextBox Grid.Row="2" Grid.Column="1" Height="23" Margin="0,8,159,0" Name="UserTextBox" VerticalAlignment="Top" Text="{Binding Path=UserName, UpdateSourceTrigger=PropertyChanged}"/>
    <Button 
                    Command="{Binding Path=LoadCommand}"
                    Content="_Load"
                    HorizontalAlignment="Right"
                    Margin="0,10,51,12" 
                    MinWidth="60" Grid.Row="3" Width="72" Grid.Column="1" />
</Grid>
</UserControl>

    Public Class MainWindowViewModel
    Inherits ViewModelBase

    Private _commands As ReadOnlyCollection(Of CommandViewModel)
    Private _ProjectsVM As AllProjectsViewModel
    Private _ProjectsSearchVM As ProjectSearchViewModel

    Public Sub New()
        MyBase.DisplayName = "Cheminator"
        _ProjectsSearchVM = New ProjectSearchViewModel

        Messenger.[Default].OfType(Of SearchResultMessage) _
            .Subscribe(Sub(param As SearchResultMessage)
                           ProjectsVM.AllProjects = ProjectsSearchVM.SearchResult
                       End Sub)
        _ProjectsVM = New AllProjectsViewModel
    End Sub

    Public ReadOnly Property ProjectsVM As AllProjectsViewModel
        Get

            If (_ProjectsVM IsNot Nothing) Then
                Return _ProjectsVM
            End If
            Return Nothing
        End Get
    End Property


    Public ReadOnly Property ProjectsSearchVM As ProjectSearchViewModel
        Get

            If (_ProjectsSearchVM IsNot Nothing) Then
                Return _ProjectsSearchVM
            End If
            Return Nothing
        End Get
    End Property

End Class

    Public Class AllProjectsViewModel
    Inherits ViewModelBase


    Private m_ProjectsList As ObservableCollection(Of xGMV_Cotation)


    Public Sub New()
        MyBase.DisplayName = "Temp AllProjectsViewModel Name" 'Strings.AllProjectsViewModel_DisplayName

    End Sub


    Public Property AllProjects() As ObservableCollection(Of xGMV_Cotation)
        Get
            Return m_ProjectsList
        End Get
        Set(ByVal value As ObservableCollection(Of xGMV_Cotation))
            m_ProjectsList = value
            OnPropertyChanged("AllProjects")
        End Set
    End Property

End Class

    结束班

1 个答案:

答案 0 :(得分：1)

每次创建ProjectSearchView用户控件时，您也会创建一个ProjectSearchViewModel。你应该从usercontrl xaml中删除以下内容。

<Grid.DataContext>
    <vm:ProjectSearchViewModel />
</Grid.DataContext>

因为你的datatemplate你不需要为ProjectSearchView设置datacontext，它已经有了正确的datacontext。

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