Intercept Silverlight DatePicker's convert from text to DateTime

Question

Hi,

I want DatePicker to convert the following text pieces to DateTime (shown in international format) so my customers can write a date in DatePickers textbox faster so it is not just DateTime.Parse I will use:

"3" to 2009-10-03
"14" to 2009-10-14
"1403" to 2009-03-14
"140310" to 2010-03-14
"14032010" to 2010-03-14

I have tried different methods to do it but they do not work. I have tried to bind DatePicker.Text/DatePicker.SelectedDate/DatePicker.DisplayDate with a custom valueconverter. But it do not work because DatePicker already have processed the text before I get to the text.

I have also tried to convert in the DatePickers TextBox.LostFocus like this:

public class CustomDatePicker : DatePicker
    {
        private DatePickerTextBox textBox;

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            textBox = this.GetTemplateChild("TextBox") as DatePickerTextBox;

            if (textBox != null)
                textBox.LostFocus += new RoutedEventHandler(textBox_LostFocus);
        }

        void textBox_LostFocus(object sender, RoutedEventArgs e)
        {
            if (textBox == null)
                return;

            DateTime result;

            //This is my method for converting my special cases, parses d, dd, mm, ddmm, ddmmyy, ddmmyyyy
            if (textBox.Text.TryParseShortcut(out result)) 
            {
                //I have also tried with this.SelectedDate/DisplayDate = result;
                textBox.Text = result.ToString("dd/MM/yyyy"); 
                return;
            }

            if (DateTime.TryParse(textBox.Text, out result))
            {
                //I have also tried with this.SelectedDate/DisplayDate = result;
                textBox.Text = result.ToString("dd/MM/yyyy");
                return; 
            }
        }
    }

Any ideas?

Answer 1

If you use Binding to bind data to your DatePicker, you could use a ValueConverter.

Quick example of date converter:

public class CustomDateValueConverter : IValueConverter
{
 public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
 {
  if (value is string)
  {
   string dateValue = (string)value;
   switch (dateValue.Length)
   {
    case 1:
    case 2:
     return new DateTime(DateTime.Now.Year, DateTime.Now.Month, System.Convert.ToInt32(dateValue)).ToString("dd/MM/yyyy");
    //...
   }
  }

  return value;
 }

 public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
 {
  // here you should implement your logic to convert your value back.

  return value;
 }
}

DatePickerTextBox control in XAML:

<controls:DatePickerTextBox Text="{Binding Path=Data, Mode=TwoWay, Converter={StaticResource CustomDateValueConverter}}" />

DatePickerTextBox in cs:

public partial class MainPage : UserControl
{
 public MainPage()
 {
  InitializeComponent();
  DataContext = new MyData() { Data = "3" };

  _textBox.LostFocus += (se, ea) =>
   {
    _textBox.DataContext = 
     new MyData() { Data = _textBox.Text };
   };
}

public class MyData
{
 public string Data { get; set; }
}

I have just made a class called MyData to use as data in this sample.

Answer 2

I think you might need to actually start will the full control source and customize that. The problem is that the text gets updated in the TextChanged event:

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
    if (this._textBox != null)
    {
        this.SetValueNoCallback(TextProperty, this._textBox.Text);
    }
}

So by the time you get to your lost focus code, the value has already been set. I was able to get around this using subclassing, but since TextChanged handles every change I'm not sure your parse method will work (Since as soon as you hit 1 number it will get changed to a date).

public class CustomDatePicker : DatePicker
{
    private TextBox textBox; 

    public override void OnApplyTemplate() 
    { 
        base.OnApplyTemplate(); 
        textBox = this.GetTemplateChild("TextBox") as TextBox; 

        if (textBox != null)
            textBox.TextChanged += new TextChangedEventHandler(textBox_TextChanged);
    }

    void textBox_TextChanged(object sender, TextChangedEventArgs e)
    {  
        if (textBox.Text == "now")             
        {                
            //I have also tried with this.SelectedDate/DisplayDate = result;                
            textBox.Text = DateTime.Now.ToShortDateString();                 
        }  
    }
}

It works for me since nothing changes until it spells the whole word, but in your case that probably won't work.