C# 从集合中删除组合框SelectedItem
基本上我对所有这些都是全新的,我正在尝试在MVVM的环境中学习C。这将是一个简单的CRUD程序,现在我正忙于从相应的集合中删除一个组合框C# 从集合中删除组合框SelectedItem,c#,wpf,xaml,mvvm,data-binding,C#,Wpf,Xaml,Mvvm,Data Binding,基本上我对所有这些都是全新的,我正在尝试在MVVM的环境中学习C。这将是一个简单的CRUD程序,现在我正忙于从相应的集合中删除一个组合框SelectedItem 相关视图模型代码: public class AlbumViewModel { private ObservableCollection<AlbumModel> albums; public AlbumViewModel() { this.albums = new Observabl
SelectedItem
相关视图模型代码:
public class AlbumViewModel
{
private ObservableCollection<AlbumModel> albums;
public AlbumViewModel()
{
this.albums = new ObservableCollection<AlbumModel>();
LoadAlbums();
}
public ObservableCollection<AlbumModel> Albums
{
get { return this.albums; }
}
public void LoadAlbums()
{
albums.Add(new AlbumModel("No Love/Deep Web", "Death Grips"));
albums.Add(new AlbumModel("In Defense of the Genre", "Say Anything"));
albums.Add(new AlbumModel("Picaresque", "The Decemberists"));
albums.Add(new AlbumModel("In Evening Air", "Future Islands"));
albums.Add(new AlbumModel("You're Gonna Miss It All", "Modern Baseball"));
}
#region RelayCommand
private RelayCommand _deleteCommand;
public ICommand DeleteCommand
{
get
{
if (_deleteCommand == null)
{
_deleteCommand = new RelayCommand(param => DeleteItem());
}
return _deleteCommand;
}
}
#endregion
#region DeleteItem()
private AlbumModel SelectedItem { get; set; }
private void DeleteItem()
{
if (SelectedItem != null)
{
this.albums.Remove(SelectedItem);
this.SelectedItem = null;
}
}
#endregion
}
public class AlbumModel : INotifyPropertyChanged
{
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
// AlbumModel members, properties, constructor
}
#region RelayCommand
public class RelayCommand : ICommand
{
// fields
readonly Action<object> _execute;
readonly Predicate<object> _canExecute;
// ctors
public RelayCommand(Action<object> execute)
: this(execute, null)
{
}
public RelayCommand(Action<object> execute, Predicate<object> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
_execute = execute;
_canExecute = canExecute;
}
// ICommand members
public bool CanExecute(object parameter)
{
return _canExecute == null ? true : _canExecute(parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested += value; }
}
public void Execute(object parameter)
{
_execute(parameter);
}
我怀疑这是我的数据绑定错误,但我很难理解错误的含义。我希望大家能从任何角度看待问题
SelectedItem
应该是公共的。绑定需要这样做DeleteItem
),而不是命令(DeleteCommand
)SelectedItem
应该是公共的。绑定需要这样做DeleteItem
),而不是命令(DeleteCommand
)重复的VM实例是什么,一个在资源中,一个作为DataContext?重复的VM实例是什么,一个在资源中,一个作为DataContext?谢谢!它们看起来很简单,所以忽略它们很尴尬,但正如我所说的,我对整个概念是全新的,学习它是一个过程。你能详细解释一下你在之前的评论中所说的“先看”是什么意思吗?复制虚拟机呢?这会很有帮助。您在
Window.DataContext
和Window.Resources
中都有VM实例。DataContext
中应该只有一个,或者您可以在参考资料中创建一个,然后在以后的DataContext
中引用它。“视图优先”的意思是,您在视图中创建视图模型的方式与之前相同(两次)。在我看来,WPF准备在所有情况下适当处理这是一种糟糕的方法。另一种选择是视图模型优先。有关详细信息,请搜索google或stack overflow。@korina:谢谢!它们看起来很简单,所以忽略它们很尴尬,但正如我所说的,我对整个概念是全新的,学习它是一个过程。你能详细解释一下你在之前的评论中所说的“先看”是什么意思吗?复制虚拟机呢?这会很有帮助。您在Window.DataContext
和Window.Resources
中都有VM实例。DataContext
中应该只有一个,或者您可以在参考资料中创建一个,然后在以后的DataContext
中引用它。“视图优先”的意思是,您在视图中创建视图模型的方式与之前相同(两次)。在我看来,WPF准备在所有情况下适当处理这是一种糟糕的方法。另一种选择是视图模型优先。有关详细信息,请搜索google或堆栈溢出。@korina:
<Window x:Class="AlbumsCRUD2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:AlbumsCRUD2.ViewModels"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:AlbumViewModel />
</Window.DataContext>
<Window.Resources>
<local:AlbumViewModel x:Key="albums" />
</Window.Resources>
<Grid>
<GroupBox Grid.Row="1" Grid.Column="1" HorizontalContentAlignment="Center" Header="View Existing">
<StackPanel>
<Label Content="Album" />
<ComboBox Name="albumComboBox"
ItemsSource="{Binding Path=Albums}"
DisplayMemberPath="AlbumName"
SelectedItem="{Binding SelectedItem, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<Label Content="Artist" />
<TextBox Text="{Binding ElementName=albumComboBox, Path=SelectedItem.ArtistName}"
IsEnabled="False" />
<Button Name="deleteBtn" Width="100" Margin="30"
Command="{Binding DeleteItem}"
Content="Delete" />
</StackPanel>
</GroupBox>
</Grid>
</Window>
System.Windows.Data Error: 40 : BindingExpression path error: 'SelectedItem' property not found on 'object' ''AlbumViewModel' (HashCode=12507741)'. BindingExpression:Path=SelectedItem; DataItem='AlbumViewModel' (HashCode=12507741); target element is 'ComboBox' (Name='albumComboBox'); target property is 'SelectedItem' (type 'Object')
System.Windows.Data Error: 40 : BindingExpression path error: 'DeleteItem' property not found on 'object' ''AlbumViewModel' (HashCode=12507741)'. BindingExpression:Path=DeleteItem; DataItem='AlbumViewModel' (HashCode=12507741); target element is 'Button' (Name='deleteBtn'); target property is 'Command' (type 'ICommand')