WPF MVVM清除文本框绑定到Listview SelectedItem

Question

我试图学习C＃mvvm和wpf，所以我决定做一个简单的项目（管理图书馆应用程序的书籍和阅读器），现在我有点迷茫了，因此我非常感谢您的帮助。 在我看来，我有一个显示读者的列表视图，以及一堆绑定到列表视图中所选项目（名称，地址等）的文本框。 列表视图绑定到使用Linq2SQL从数据库表（阅读器）创建的可观察阅读器集合。

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，如果我在单击按钮时尝试执行一些命令，则列表视图的“选定项目”似乎为空。

• 当我单击清除按钮时，如果我在所选项目（阅读器）上有一个断点，则表明它的间隔为空/空，但文本框没有清除； 如果在Clear方法中使用SelectedReader属性，并为其属性分配空白，则列表视图中的所选项目也会被清除（因为它绑定到Reader的FullName属性）

• 我在添加新的阅读器以及保存更改方面还有其他问题，并且我认为这是由于错误的linq查询引起的，但是我希望我可以解决当前问题，然后继续进行。

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
        };
    }

视图：

     <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

您是否尝试过将文本框的文本属性的Binding直接设置为ViewModel的SelectedReader -Property？ 所以不用写这个：

<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}" ... />