从 sql 到文本框的数据绑定不起作用

Question

有一个带有文本框的简单 WPF 窗口。在这个窗口中，我想显示一个用户 ID。这是 winforms 中的一个如此简单的过程，但我似乎无法在 XAML 中完全理解它。 该代码是一个简单的类 - 用户列表如下......

public class User
    {
        private string userId;
        private string employeeNumber;
        ...

        public User()
        { }

        public string UserId
        {
            get
            { 
            return userId;
            }
            set
            {
                userId = value;
            }
        }


        public string EmployeeNumber
        {
            get
            {
                return employeeNumber;
            }
            set
            {
                employeeNumber = value;
            }
        }
    }
    ...

wpf 窗口的 xaml 是...

<Window
    ...
    <Window.Resources></Window.Resources>
    <Grid>
        <Label x:Name="lblUserId" Content="User Id" HorizontalAlignment="Left" Margin="84,76,0,0" VerticalAlignment="Top"/>
        <Label x:Name="lblEmployeeNumber" Content="Employee Number" HorizontalAlignment="Left" Margin="84,106,0,0" VerticalAlignment="Top"/>
        <TextBox x:Name="tbUserId" HorizontalAlignment="Left" Height="23" Margin="200,76,0,0" TextWrapping="Wrap"  VerticalAlignment="Top" Width="120" />
        <TextBox x:Name="tbEmployeeNumber" HorizontalAlignment="Left" Height="23" Margin="200,106,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120" />
    </Grid>
</Window>

当窗口加载后，这段代码被执行。

public partial class winTest : Window
{
    public winTest()
    {
        InitializeComponent();
    }

    private User user;
    private List<User> userList;
    private List<Permissions> permissionsList;

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
            string userId = "1234";
            user = UserDB.GetUserInfo(userId);
    }

}
...

GetUserInfo 的代码是

public static User GetUserInfo(string userID)
    {
        User user = new User();
        SqlConnection connection = BusinessDB.GetConnection();
        string selectStatement = "SELECT userid, empno, FROM employees " +
        "WHERE userid = @UserID";
        SqlCommand selectCommand = new SqlCommand(selectStatement, connection);
        selectCommand.Parameters.AddWithValue("userid", userID);
        try
        {
            connection.Open();
            //SqlDataReader reader = selectCommand.ExecuteReader();
            SqlDataReader reader = selectCommand.ExecuteReader(CommandBehavior.SingleRow);
            if (reader.Read())
            {
                if (reader["userid"] == DBNull.Value)
                {
                    user.UserId = "";
                }
                else
                {
                    user.UserId = (reader["userid"]).ToString();
                }

                if (reader["empno"] == DBNull.Value)
                {
                    user.EmployeeNumber = "";
                }
                else
                {
                    user.EmployeeNumber = reader["empno"].ToString();
                }
        }
    return user 
    }   
 ...

单步执行代码显示用户确实填充了正确的信息 - 它是让我知道的绑定部分。上面的 xaml 没有列出任何绑定，因为我已经尝试将它绑定到除了我的狗鼻子之外的所有东西，但我仍然得到空文本框。 任何人都可以帮助一个wpf新手吗？非常感谢。

Answer 1

1. 您需要将您的 User 设为公共属性，而不是私有字段：

   public User User { get; set }
   

2. 如果您希望您的绑定响应User 值的变化，您的Window 类需要实现INotifyPropertyChanged。

   public partial class winTest : Window, INotifyPropertyChanged
   {
       public event PropertyChangedEventHandler PropertyChanged;
   
       private void NotifyPropertyChanged(string propertyName)
       {
           if (PropertyChanged != null)
           {
               PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
           }
       }
   
       // <your other winTest code goes here>
   }
   

3. 您的绑定应如下所示：

   <TextBox x:Name="tbUserId"
            Text="{Binding User.UserId}"
            HorizontalAlignment="Left"
            Height="23"
            Margin="200,76,0,0"
            TextWrapping="Wrap"
            VerticalAlignment="Top"
            Width="120" />
   

Answer 2

正如 devuxer 所说，确保将您的公共属性重写为：

public string UserId { get; set; }
public string EmployeeNumber { get; set; }

在你的 Window_loaded() 上试试这个方法；

private void Window_Loaded(object sender, RoutedEventArgs e)
{
        string userId = "1234";
        user = UserDB.GetUserInfo(userId);
        tbUserId.Text = user.UserId;
        tbEmployeeNumber.Text = user.tbEmployeeNumber;

}