如何使用 MVVM 体系结构在 WPF 中设置组合框值

Question

我在WPF MVVM架构中创建了一个POC。我在其中使用了组合框控件，您可以在下面的代码中看到。

<ComboBox Name="DeptCombo" Grid.Row="4" Grid.Column="1" ItemsSource="{Binding DepartmentList,Mode=TwoWay}" SelectedItem="{Binding Path=CurrentDepartment,Mode=TwoWay}" DisplayMemberPath="DepartmentName">
</ComboBox>

这里当前部门是部门类的属性。

一切都很好，我填充了那个组合，将该组合值保存在数据库中，但我面临的唯一问题是，我无法在该组合中设置保存的数据库值。我没有得到任何解决方案。请帮助我。

Answer 1

添加UpdateSourceTrigger

SelectedItem="{Binding Path=CurrentDepartment,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"

Е 代码应如下所示：

class ViewModel: INotifyPropertyChanged
{
public ObservableCollection<string> Datas { get; set; } = new ObservableCollection<string>()
{
"FF", "AA", "BB"
};
private string currentItem;
public string CurrentItem
{
get => currentItem;
set
{
currentItem = value;
OnPropertyChanged("CurrentItem");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName]string prop="")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(prop));
}
}

模型示例： 人物模型.cs：

class PersonModel
{
public string Name { get; set; }
public int Age { get; set; }
}

视图模型.cs：

class ViewModel: INotifyPropertyChanged
{
public ObservableCollection<PersonModel> Datas { get; set; } = new ObservableCollection<PersonModel>()
{
new PersonModel(){Age = 10, Name="Tom"},
new PersonModel(){Age = 10, Name="Mark"},
};
private PersonModel currentItem;
public PersonModel CurrentItem
{
get => currentItem;
set
{
currentItem = value;
OnPropertyChanged("CurrentItem");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName]string prop="")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(prop));
}
}

MainWindow.xaml：

<ComboBox ItemsSource="{Binding Datas}" SelectedItem="{Binding CurrentItem, UpdateSourceTrigger=PropertyChanged}"
Height="100" Width="100">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}"/>
<TextBlock Text="{Binding Age}"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>

Answer 2

部门类 ：

public class Department : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertychanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
private int id;
public int Id
{
get { return id; }
set { id = value; OnPropertychanged("Id"); }
}
private string departmentName;
public string DepartmentName
{
get { return departmentName; }
set { departmentName = value; OnPropertychanged("DepartmentName"); }
}
private bool isActive;
public bool IsActive
{
get { return isActive; }
set { isActive = value; OnPropertychanged("IsActive"); }
}
}

查看型号 ：

private ObservableCollection<Department> departmentList;
public ObservableCollection<Department> DepartmentList
{
get { return departmentList; }
set { departmentList = value; OnPropertyChanged("DepartmentList"); }
}
private Department currentDepartment;
public Department CurrentDepartment
{
get { return currentDepartment; }
set { currentDepartment = value; OnPropertyChanged("CurrentDepartment"); }
}
private void DepartmentPop()
{
DepartmentList = new ObservableCollection<Department> 
(objDepartmentService.GetAll());
}