c# - 按钮 IsEnabled 永远不会改变

Question

这是我的 Button 声明，用 .xaml 文件编写:

<dxlc:LayoutGroup Orientation="Horizontal"  Margin="5,15,0,5">
    <Grid MinWidth="100">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Button 
            IsEnabled="{Binding IsSearchCriteriaHasValue}" 
            Content="Search" 
            MaxHeight="25" 
            MaxWidth="70" 
            ClipToBounds="True"  
            VerticalAlignment="Center"
            HorizontalAlignment="Center" 
            HorizontalContentAlignment="Center"                  
            VerticalContentAlignment="Center" 
            Command="{Binding SearchCommand}"/>
    </Grid>
</dxlc:LayoutGroup>

无论用户是否在搜索按钮旁边的搜索框中键入了任何搜索文本，该函数都会返回 true/false。该函数在另一个 .cs 文件中:

public bool isButtonEnabled
{
    return (SearchBox.Selection.Count > 0);
}

问题是 isEnabled 的值永远不会改变，它保持为真，即按钮始终保持启用状态，或者如果我更改 > 符号，按钮始终保持禁用状态。有什么建议吗？

Answer 1

IsSearchCriteriaHasValue 需要引发它更改的事件，您可以使用 INotifyPropertyChanged 接口(interface)来实现:

public class Customer : INotifyPropertyChanged
{
    // INotifyPropertyChanged members
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, e);
        }
    }

    // Your property
    private string _Name;

    public string Name
    {
        get
        {
            return _Name;
        }
        set
        {
           _Name = value;
           OnPropertyChanged(new PropertyChangedEventArgs("Name"));
        }
    }
}