基于通过路由命令对文本框进行验证的文本块的绑定可见性

Question

我正在编写一个简单的应用程序，UI有两个文本框，分别表示用户名和密码；密码和提交信息的按钮。我想使用路由命令，而不是按钮点击事件。

用户名应仅包含字母数字字符，如果用户输入任何其他特殊字符，则应显示一个文本，说明输入的无效字符。所以我想根据对Username文本框字段进行的验证来绑定该文本块的可见性和内容。有人能帮助我如何做到这一点吗？

下面是我制作的代码，但它并没有按预期工作。有人能帮我哪里做错了吗？

在我的主窗口下方.xaml

using System.Windows;
using System.Windows.Input;
using System.ComponentModel;

namespace ExcelUtility
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    ViewModel viewModelObj = new ViewModel();
    public MainWindow()
    {
        InitializeComponent();
    }
    void navigatePageExecuted(object target, ExecutedRoutedEventArgs e)
    {
        SubmitUserDetails(txtUserName.Text + ";" + txtPassword);
    }
    void navigatePageCanExecute(object sender, CanExecuteRoutedEventArgs e)
    {
         if (!string.IsNullOrWhiteSpace(txtUserName.Text))
        {
            viewModelObj.Username = txtUserName.Text;
        }
        e.CanExecute = viewModelObj.VaidUserName;        }
    private void SubmitUserDetails(string credentials)
    {
        this.Cursor = Cursors.Wait;
        prgValidate.Visibility = Visibility.Visible;
        MainGrid.IsEnabled = false;
        BackgroundWorker worker = new BackgroundWorker();
        worker.DoWork += worker_DoWork;
        worker.RunWorkerCompleted += worker_RunWorkerCompleted;
        worker.RunWorkerAsync(credentials);
    }
    void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        prgValidate.Visibility = Visibility.Collapsed;
        string Result = (string)e.Result;
        MessageBox.Show(Result); //Here I need to call some other functions based on return value for simplicity i have changed
    }
    void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        string[] credentials = e.Argument.ToString().Split(';');
        e.Result = viewModelObj.validateCredentials(credentials[0], credentials[1]);
    }
}

}

这是我的xaml

<Window x:Class="ExcelUtility.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:ExcelUtility"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <local:BoolToVisibleOrHidden x:Key="BoolToVisibilityConverter"/>
</Window.Resources>
<Window.CommandBindings>
    <CommandBinding Command="{x:Static local:CommandsLibrary.navigatePageCommand}" Executed="navigatePageExecuted" CanExecute="navigatePageCanExecute"/>
</Window.CommandBindings>
<Grid Name="MainGrid">
    <TextBlock Height="23" HorizontalAlignment="Left" Margin="40,44,0,0" Name="tbUserName" Text="Username" VerticalAlignment="Top" />
    <TextBox Height="23" HorizontalAlignment="Left" Margin="136,42,0,0" Name="txtUserName" VerticalAlignment="Top" Width="163" Text="{Binding Username, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" />
    <TextBlock Height="23" HorizontalAlignment="Left" Margin="138,19,0,0" Name="tbNotify" Text="{Binding Notification, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Width="161" Visibility="{Binding NotVaidUserName,Converter={StaticResource BoolToVisibilityConverter}}" />
    <TextBox Height="23" HorizontalAlignment="Left" Margin="138,98,0,0" Name="txtPassword" VerticalAlignment="Top" Width="161" />
    <TextBlock Height="23" HorizontalAlignment="Left" Margin="44,107,0,0" Name="tbPassword" Text="Password" VerticalAlignment="Top" Width="65" />
    <Button Command="{x:Static local:CommandsLibrary.navigatePageCommand}" Content="Submit" Height="23" HorizontalAlignment="Left" Margin="172,167,0,0" Name="btnSubmit" VerticalAlignment="Top" Width="109" />
    <ProgressBar Height="24" IsIndeterminate="True" Visibility="Collapsed"  HorizontalAlignment="Left" Margin="52,232,0,0" Name="prgValidate" VerticalAlignment="Top" Width="257" />
</Grid>

这是我的视图型号

using System;
using System.Text.RegularExpressions;
using System.ComponentModel;
using System.Windows.Data;
using System.Windows;
namespace ExcelUtility
{
  public class ViewModel : INotifyPropertyChanged
  {
    public event PropertyChangedEventHandler PropertyChanged;
    private bool _notVaidUserName;
    public bool NotVaidUserName
    {
        get { return _notVaidUserName; }
        set
        {
            _notVaidUserName = value;
            RaisePropertyChanged("NotVaidUserName");
        }
    }
    private string notification;
    public string Notification
    {
        get
        {
            return notification;
        }
        set
        {
            if (notification != value)
            {
                notification = value;
                RaisePropertyChanged("Notification");
            }
        }
    }
    private string username;
    public string Username
    {
        get
        {
            return username;
        }
        set
        {
            if (username != value)
            {
                username = value;
                NotVaidUserName = VaidateUserName(username);
                RaisePropertyChanged("Username");
            }
        }
    }
    public bool VaidateUserName(string strUsername)
    {
        bool bValidUserName = false;            
        if (!string.IsNullOrWhiteSpace(strUsername))
        {
            if (new Regex(@"^[a-zA-Z0-9]*$").IsMatch(strUsername))
            {
                bValidUserName = true;
                if (strUsername.Length > 7)
                {
                    Notification = "Max allowed key length is 6";
                    bValidUserName = false;
                }
            }
            else
            {
                Notification = "No special characters allowed";
            }
        }
        return bValidUserName;
    }
    public string validateCredentials(string Username, string Password)
    {
        return "Valid Credentials";
    }
    private void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}
class BoolToVisibleOrHidden : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        object returnvalue = new object();
        returnvalue = (bool)value ? Visibility.Visible : parameter != null ? Visibility.Collapsed : Visibility.Hidden;
        return returnvalue;
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return (Visibility)value == Visibility.Visible;
    }
}

}

非常感谢。Durga

Answer 1

您的代码不工作的原因是您没有设置视图的数据上下文。我喜欢在xaml中设置数据上下文，因为它将在VS中为您的绑定指令提供自动完成功能。在根节点上，添加属性

DataContext="{Binding RelativeSource={RelativeSource Self}}"

这将把窗口本身设置为您的数据上下文，允许您的命令工作。但是，文本框上的绑定表达式将失败。您已经将ViewModel逻辑拆分为视图和ViewModel。

我会把你的代码完全移到ViewModel中，并使用

DataContext="{Binding RelativeSource={RelativeSource Self}, Path=ViewModel}"

作为数据上下文。那么，在视图的代码后面，您所拥有的唯一代码将是类似的代码

namespace ExcelUtility
{
    public partial class MainWindow : Window
    {
        private ViewModel viewModel;
        public MainWindow()
        {
            InitializeComponent();
        }
        public ViewModel ViewModel { get { return viewModel ?? (viewModel = new ViewModel()); } }
    }
}

绑定工作后，您将不必在视图模型中设置UserName或Password（就像在navigatePageCanExecute和navigatePageExecuted方法中所做的那样），因为绑定将为您设置它。我不确定你的命令库。你没有把它包括在这个例子中。

这应该会让你开始弄清楚剩下的

我希望它能帮助