c# - WPF Bound Editable Combobox 在文本更改时不更改 ID

Question

我不确定 bind 的正确方法是什么combobox control是我的view model .

我正在使用 MVVM 方法，所以在我的 viewmodel 中我正在加载所有 CDType数据并将其源与实际记录属性结合在一起model.CDType.id和 model.CDType.name .

当我更改文本时会发生什么？ - 我保留我的旧 id(来自加载例程)并从组合框绑定(bind)中获取新的文本值，因此始终覆盖现有记录而不是创建新记录。

如果文本不在列表中，如何让我的组合框将 id 设置为 0/undefined？ (手动？-有点蹩脚)

任何事情都会有所帮助-谢谢!

TL;DR: 可编辑组合框不会在文本更改时更新 ID。

示例 Xaml 绑定(bind):

<ComboBox x:Name="ddlCDType"    
          IsTextSearchEnabled="True"     
          IsTextSearchCaseSensitive="False"     
          StaysOpenOnEdit="True"    
          TextSearch.TextPath="Name"     
          ItemsSource="{Binding CDTypes}"    
          SelectedValue="{Binding Assignment.CDType.ID}"     
          Text="{Binding Assignment.CDType.Name,     
          UpdateSourceTrigger=PropertyChanged,    
          NotifyOnValidationError=True,     
          ValidatesOnDataErrors=True}"      
          DisplayMemberPath="Name"     
          SelectedValuePath="ID"     
          IsEditable="True"     
          HorizontalAlignment="Left"     
          Margin="98,10,0,0"     
          VerticalAlignment="Top"     
          Width="136" />

Answer 1

据我所知，当手动更改所选 ComboBox 项目的名称并且此名称未出现在 ComboBox ItemSource 中时，您需要更新上一个最后选择的值。这是我的建议，它是您的 ComboBox 控件数据绑定(bind)和 ViewModel 中定义的逻辑的组合。

绑定(bind)说明

由于 ComboBox ItemsSource 是 Cd 的集合(ComboModels 的集合)，因此 TextSearch.TextPath binding 应定义为 CDType.Name，其中 CdType 是 ComboModel 中定义的描述子模型的属性，Name 是描述子模型的实际搜索路径。

ComboBox Text 属性绑定(bind)到 AssignmentText 属性以在组合失去焦点时触发更新逻辑(如绑定(bind)中定义的那样)。

如您的示例代码中定义的那样，ItemsSource 是微不足道的。

选定的值将更新整个模型(以防我们更改选定的值名称)。

由于 ComboBox ItemsSource 是 Cd 的集合(我们称之为 ComboModel)DisplayMemberPath binding 应定义为 CDType.Name，其中 CdType 是 ComboModel 中定义的描述子模型的属性，Name 是描述子模型的实际搜索路径。

Xaml 代码:

        <Grid VerticalAlignment="Bottom">
        <Grid.DataContext>
            <comboBoxWhenNoAnySelectedHelpAttempt:ComboboxDataContext/>
        </Grid.DataContext>
        <StackPanel Orientation="Vertical">
            <ComboBox x:Name="ddlCDType"    
                      IsTextSearchEnabled="True"     
                      IsTextSearchCaseSensitive="False"     
                      StaysOpenOnEdit="True"    
                      TextSearch.TextPath="CDType.Name"
                      Text="{Binding AssignmentText,     
                      UpdateSourceTrigger=LostFocus, Mode=TwoWay,
                      ValidatesOnDataErrors=True}"
                      ItemsSource="{Binding CDTypes}"    
                      SelectedValue="{Binding Assignment}"     
                      DisplayMemberPath="CDType.Name"     
                      IsEditable="True"     
                      HorizontalAlignment="Left"     
                      Margin="98,10,0,0"     
                      VerticalAlignment="Top"     
                      Width="136" />
            <!--added to see changes in updated combo box item-->
            <TextBlock >
                      <Run Text="Name:"/>
                      <Run Text="{Binding Assignment.CDType.Name, UpdateSourceTrigger=PropertyChanged}"></Run>
                      <Run Text="Id:"/>
                      <Run Text="{Binding Assignment.CDType.ID, UpdateSourceTrigger=PropertyChanged}"></Run>
            </TextBlock>
        </StackPanel>
    </Grid>

虚拟机代码

public class ComboboxDataContext:BaseObservableObject
{
    private ObservableCollection<ComboModel> _cdTypes;
    private ComboModel _assignment;
    private string _assignmentText;
    private string _lastAcceptedName;


    public ComboboxDataContext()
    {
        CDTypes = new ObservableCollection<ComboModel>
        {
            new ComboModel
            {
                CDType = new ComboModelSubModel
                {
                    Name = "Cd-1",
                    ID = "1",
                },
            },
            new ComboModel
            {
                CDType = new ComboModelSubModel
                {
                    Name = "Cd-2",
                    ID = "2",
                }
            },
            new ComboModel
            {
                CDType = new ComboModelSubModel
                {
                    Name = "Cd-3",
                    ID = "3",
                },
            },
            new ComboModel
            {
                CDType = new ComboModelSubModel
                {
                    Name = "Cd-4",
                    ID = "4",
                }
            }
        };
        Assignment = CDTypes.FirstOrDefault();
    }

    public ObservableCollection<ComboModel> CDTypes
    {
        get { return _cdTypes; }
        set
        {
            _cdTypes = value;
            OnPropertyChanged();
        }
    }

    public ComboModel Assignment
    {
        get { return _assignment; }
        set
        {
            if (value == null)
                _lastAcceptedName = _assignment.CDType.Name;
            _assignment = value;
            OnPropertyChanged();
        }
    }

    //on lost focus when edit is done will check and update the last edited value
    public string AssignmentText
    {
        get { return _assignmentText; }
        set
        {
            _assignmentText = value;
            OnPropertyChanged();
            UpDateSourceCollection(AssignmentText);
        }
    }

    //will do the the update on combo lost focus to prevent the 
    //annessasary updates (each property change will make a lot of noice in combo)
    private void UpDateSourceCollection(string assignmentText)
    {
        var existingModel = CDTypes.FirstOrDefault(model => model.CDType.Name == assignmentText);
        if (existingModel != null) return;
        if (_lastAcceptedName == null)
        {
            CDTypes.Add(new ComboModel{CDType = new ComboModelSubModel{ID = string.Empty, Name = assignmentText}});
        }
        else
        {
            var existingModelToEdit = CDTypes.FirstOrDefault(model => model.CDType.Name == _lastAcceptedName);
            if(existingModelToEdit == null) return;
            existingModelToEdit.CDType.Name = assignmentText;
            existingModelToEdit.CDType.ID = string.Empty;
        }

    }
}

public class ComboModel:BaseObservableObject
{
    private ComboModelSubModel _cdType;

    public ComboModelSubModel CDType
    {
        get { return _cdType; }
        set
        {
            _cdType = value;
            OnPropertyChanged();
        }
    }
}

public class ComboModelSubModel:BaseObservableObject
{
    private string _id;
    private string _name;

    public string ID
    {
        get { return _id; }
        set
        {
            _id = value;
            OnPropertyChanged();
        }
    }

    public string Name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }
}

BaseObservableObject 代码

    /// <summary>`enter code here`
/// implements the INotifyPropertyChanged (.net 4.5)
/// </summary>
public class BaseObservableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        var handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }

    protected virtual void OnPropertyChanged<T>(Expression<Func<T>> raiser)
    {
        var propName = ((MemberExpression)raiser.Body).Member.Name;
        OnPropertyChanged(propName);
    }

    protected bool Set<T>(ref T field, T value, [CallerMemberName] string name = null)
    {
        if (!EqualityComparer<T>.Default.Equals(field, value))
        {
            field = value;
            OnPropertyChanged(name);
            return true;
        }
        return false;
    }
}

问候。