WPF 中的验证 - 自定义验证规则或 IDataErrorInfo

自定义验证规则和 IDataErrorInfo 是 WPF 中常用的验证技术，它们可以帮助我们在用户输入数据时进行验证，并及时地提供错误信息。本文将介绍如何 一篇关于 WPF 中自定义验证规则和 IDataErrorInfo 的文章，并提供相应的案例代码。

xaml
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Login" Height="250" Width="350">
    
        
            
            
        
        
            
            
            
            
        
        
        
        
        
        
        
    

csharp
public class LoginViewModel : INotifyPropertyChanged, IDataErrorInfo
{
    private string _username;
    private string _password;
    private string _error;
    public string Username
    {
        get { return _username; }
        set
        {
            _username = value;
            OnPropertyChanged(nameof(Username));
        }
    }
    public string Password
    {
        get { return _password; }
        set
        {
            _password = value;
            OnPropertyChanged(nameof(Password));
        }
    }
    public string Error
    {
        get { return _error; }
        set
        {
            _error = value;
            OnPropertyChanged(nameof(Error));
        }
    }
    public string this[string columnName]
    {
        get
        {
            if (columnName == nameof(Username))
            {
                if (string.IsNullOrEmpty(Username))
                    return "Username is required.";
            }
            if (columnName == nameof(Password))
            {
                if (string.IsNullOrEmpty(Password))
                    return "Password is required.";
            }
            return null;
        }
    }
    public ICommand LoginCommand { get; }
    // 省略其他代码...
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

csharp
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new LoginViewModel();
    }
}