TextBox控件未更新.Text属性

Question

Can anyone shed light on this issue?

I have a bunch of controls creating in a class

public static TextBox uname = new TextBox { PlaceholderText = "Username", Margin = new Thickness(0, 5, 0, 0), Text = MainPage.UNAME };

When I call the database to update the UNAME field on the mainpage, it does and I can print the new value. However, The textBox that is shown above which resides in a different class does not update to the new value.

I've tried initializing this textbox after the database gets the values but no luck.

Any help is appreciated.

Answer 1

The uname TextBox is instantiated and assigned when your Page is created. Although you call the database to update the MainPage.UNAME but you have not changed the pointer content of uname.Text . The easy way you can set uname.Text directly like uname.Text = MainPage.UNAME .

You can also use xaml data Binding like code behind.

MainPage.xaml.cs

 public ViewModel viewModel { get; set; }      
 public MainPage()
 {          
     this.InitializeComponent();
     this.viewModel = this.DataContext as ViewModel;

 }

 private void MyButton_Click(object sender, RoutedEventArgs e)
 {   
     viewModel.Uname = MainPage.UNAME;
 }

MainPage.xaml

<TextBox
    Margin="0,0,5,0"
    PlaceholderText="User Name"
    Text="{Binding Path=Uname}" />

ViewModel.cs

public event PropertyChangedEventHandler PropertyChanged;
private string uname;
public string Uname
{
    get
    {
        return uname;
    }

    set
    {
        uname = value;
        OnPropertyChanged();
    }
}

public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
    PropertyChangedEventHandler eventHandler = this.PropertyChanged;
    if (eventHandler != null)
    {
        eventHandler(this, new PropertyChangedEventArgs(propertyName));
    }
}

Answer 2

I figured out a way around it.

I changed this line:

public static TextBox uname = new TextBox { PlaceholderText = "Username", Margin = new Thickness(0, 5, 0, 0), Text = MainPage.UNAME };

To this:

public static TextBox uname = new TextBox { PlaceholderText = "Username", Margin = new Thickness(0, 5, 0, 0) };

Then put all my Text assignments in the initialization method.

ex. , uname.Text = MainPage.UNAME

Then.. I called the init after the DB call and poof it worked!