Question

我有一个带有一些项目和文本块的组合框，我希望如果用户从组合框中选择让我们坐着Item3，那么文本块将是可见的，否则是不可见的。

我想用mvvm做这个（我是这个架构的新手），我添加了一些MessageBox来检查它是否进入if条件并显示MessageBox但文本块总是不可见的，这里是我的代码：

XAML：

<ComboBox x:Name="product_combobox" IsEditable="False" IsReadOnly="True"  Height="24" Margin="155,106,155,0"  HorizontalAlignment="Center" VerticalAlignment="Top"  Width="210" ItemsSource="{Binding MyItems}" SelectedIndex="{Binding YourIndexProperty}" SelectedItem="{Binding SelectedItem}" />

<TextBlock x:Name="version_textBlock" Visibility="{Binding VersionVisibility}"  Height="20" Margin="155,144,155,0" TextWrapping="Wrap" HorizontalAlignment="Center" Text="Select Sasa version:" VerticalAlignment="Top" FontFamily="Moire ExtraBold" RenderTransformOrigin="0.582,0.605" Width="210" FontWeight="Bold" />

ViewModel.cs：

public ObservableCollection<string> MyItems { get; set; }
        public string _mySelectedItem;
        public Visibility _isEnable;

        public Page1VM()
        {
            this.DisplayMessageCommand = new RelayCommand(this.DisplayMessage);
            MyItems = new ObservableCollection<string>()
            {
                 "--Product--",
                "Item1",
                "Item2",
                "Item3"
            };
            _mySelectedItem = "--Product--";
            _isEnable = Visibility.Hidden;//<--------this for hiding the textblock when page load
        }

public Visibility VersionVisibility
        {
            get { return _isEnable; }
            set { _isEnable = value; }
        }



        public string SelectedItem
        {
            get { return _mySelectedItem; }
            set
            {
                _mySelectedItem = value;

                if (value.Equals("Item3"))
                {
                    VersionVisibility = Visibility.Visible;

                    MessageBox.Show("test");
                }
            }
        }

Answer 1

您需要告诉视图在viewmodel中属性的值已更改，并且应该读取该值。在viewmodel中实现inotifypropertychanged。在这里提高房产价格：

Public Visibility VersionVisibility
        {
            get { return _isEnable; }
            set { _isEnable = value; RaisePropertyChanged();}
        }

这是一个基本的viewmodel类，你可以从中继承你的viewmodel。

public class BaseViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

如果选择了某个组合框项目，则使文本块可见 - MVVM

1 个答案: