Question

我正在尝试了解C＃mvvm和wpf，所以我决定制作一个简单的项目（一本书和读者管理图书馆的应用程序），现在我有点迷失，所以我真的很感激一些帮助。在我看来，我有一个列表视图显示读者，以及一组文本框绑定到列表视图的选定项目（名称，地址等）。 listview绑定到使用Linq2SQL从数据库表（读者）创建的可观察的读者集合。

在文本框下方，我有几个按钮（清除/添加/保存/删除）。

我遇到的问题是＆＃34;所选项目＆＃34;如果我在单击按钮时尝试执行某些命令，则列表视图似乎为null。

当我点击清除按钮时，如果我在所选项目（阅读器）上有一个断点，它会显示它为空/空间隔，但文本框不清楚; 如果在Clear方法中使用了SelectedReader属性，并为其属性分配了空格，则列表视图中的所选项也会清除（因为它绑定到Reader的FullName属性）
我在添加新阅读器和保存更改方面存在其他问题，我认为是因为错误的linq查询，但我希望我能解决当前的问题并继续前进。

我该怎么办？

视图模型

  public class MainWindowViewModel : ViewModelBase
{
    private Reader selectedReader;       

    private ObservableCollection<Reader> readerList;

    public MainWindowViewModel()
    {
        SelectedReader = new Reader()
                        {
                            FullName = "",
                            SerialNumber = "",
                            IdNumber = "",
                            Adress = "",
                            AltContactMethods = ""
                        };

        BookDBDataContext rdb = new BookDBDataContext();
        ReadersList = new ObservableCollection<Reader>(rdb.Readers);

        AddR = new TblQryCommand(AddToDb);
        EditR = new TblQryCommand(EditToDb);
        DeleteR = new TblQryCommand(DeleteFromDb);
        ClearR = new TblQryCommand(ClearReaderFields);
    }

    public TblQryCommand AddR { get; private set; }
    public TblQryCommand EditR { get; private set; }
    public TblQryCommand DeleteR { get; private set; }
    public TblQryCommand ClearR { get; private set; }

    //Reader List
    public ObservableCollection<Reader> ReadersList
    {
        get { return readerList; }
        set
        {
            if (readerList != value)
            {
                readerList = value;
                RaisePropertyChanged();
            }
        }
    }

    public Reader SelectedReader
    {
        get { return selectedReader; }
        set
        {
            if (selectedReader != value)
            {
                selectedReader = value;
                RaisePropertyChanged();
            }
        }
    }

    public void AddToDb()
    {
        BookDBDataContext db = new BookDBDataContext();
        Reader r = new Reader
        {
            FullName = SelectedReader.FullName,
            SerialNumber = SelectedReader.SerialNumber,
            IdNumber = SelectedReader.IdNumber,
            Adress = SelectedReader.Adress,
            AltContactMethods = SelectedReader.AltContactMethods
        };

        db.Readers.InsertOnSubmit(r);
        db.Readers.Context.SubmitChanges();
    }

    public void DeleteFromDb()
    {

    }

    public void EditToDb()
    {

    }

    public void ClearReaderFields()
    {
        SelectedReader = new Reader
        {
            Id = 0,
            FullName = string.Empty,
            SerialNumber = string.Empty,
            IdNumber = string.Empty,
            Adress = string.Empty,
            AltContactMethods = string.Empty
        };
    }

查看：

     <ListView Name="listviewReaders" ItemsSource="{Binding ReadersList}" SelectedItem="{Binding SelectedReader,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Width="140" Height="180" Margin="10,68,492,281">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding FullName}" />
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>


  <TextBox x:Name="txtBxFullName" HorizontalAlignment="Left" Height="22"  Margin="211,68,0,0" TextWrapping="Wrap" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.FullName, Mode=TwoWay, UpdateSourceTrigger=Explicit}" VerticalAlignment="Top" Width="315"/>
        <TextBox x:Name="txtBxSerialNumber" HorizontalAlignment="Left" Height="22"  Margin="211,95,0,0" TextWrapping="Wrap" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.SerialNumber, Mode=TwoWay, UpdateSourceTrigger=Explicit}" VerticalAlignment="Top" Width="315"/>
        <TextBox x:Name="txtBxIdNumber" HorizontalAlignment="Left" Height="22"  Margin="211,122,0,0" TextWrapping="Wrap" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.IdNumber, Mode=TwoWay, UpdateSourceTrigger=Explicit}" VerticalAlignment="Top" Width="315"/>
        <TextBox x:Name="txtBxAdress" HorizontalAlignment="Left" Height="22"  Margin="211,149,0,0" TextWrapping="Wrap" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.Adress, Mode=TwoWay, UpdateSourceTrigger=Explicit}" VerticalAlignment="Top" Width="315"/>
        <TextBox x:Name="txtBxAltContactMethods" HorizontalAlignment="Left" Height="22"  Margin="211,176,0,0" TextWrapping="Wrap" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.AltContactMethods, Mode=TwoWay, UpdateSourceTrigger=Explicit}" VerticalAlignment="Top" Width="315"/>

 <Button x:Name="btnReader_Clear" Content="Clear" Command="{Binding ClearR}" HorizontalAlignment="Left" Margin="211,228,0,0" VerticalAlignment="Top" Width="75"/>
    <Button x:Name="btnReader_Save" Content="Save" Command="{Binding EditR}" HorizontalAlignment="Left" Margin="291,228,0,0" VerticalAlignment="Top" Width="75"/>
    <Button x:Name="btnReader_Add" Content="Add New" Command="{Binding AddR}" HorizontalAlignment="Left" Margin="371,228,0,0" VerticalAlignment="Top" Width="75"/>
    <Button x:Name="btnReader_Delete" Content="Delete" Command="{Binding DeleteR}" HorizontalAlignment="Left" Margin="451,228,0,0" VerticalAlignment="Top" Width="75"/>

Answer 1

您是否曾尝试将文本框的Text-Property的Binding直接设置为ViewModel＆＃39; s SelectedReader - 属性？所以不要写这个：

<TextBox x:Name="txtBxFullName" Text="{Binding ElementName=listviewReaders, Path=SelectedItem.FullName, Mode=TwoWay, UpdateSourceTrigger=Explicit}" ... />

你会写：

<TextBox x:Name="txtBxFullName" Text="{Binding Path=SelectedReader.FullName, Mode=TwoWay, UpdateSourceTrigger=Explicit}" ... />

WPF MVVM清除文本框绑定到Listview SelectedItem

1 个答案: