普通 TextBox 中的自动文本校正

Question

I want to implement an auto correction in some of the TextBox es in my application. What I mean by that is when user enters a text, after a few seconds, the text should be passed to method, get corrected and passed back to the text box.

At the moment I have a very basic procedure for the correction. My TextBoxes are supposed to get a measurement value from user (Such as 1.25 mA , 1.25uA , .666 A ).

Imagine I have the correction method called CorrectValue :

private void CorrectValue(TextBox tb)
{
   tb.Text = tb.Text.Trim().Remove('', string.Empty);
   //Actual correction is going to be much more complicated
}

So what would be the best approach fo doing so? what kind of events should be rised? how to count the seconds user spent writing in the TextBox?

Answer 1

The best place for validating the input is the event Validating of the TextBox control. If the entered value isn't valid, set e.Cancel in that event to false.

Answer 2

For me, the best event for such corrections / input validating is the Validating event.

Problem with TextChanged is, it occurs while typing and you can't be sure the user has completed his input.

Answer 3

The most basic implementation would be for you to use the TextChanged event of the Textbox. In this event you can your method CorrectValue(). As a parameter for the function you can cast the 'sender' parameter of the event to TextBox and pass it on to your method.

Edit: For counting the time you could set a Timer and fire it every 0.5second for example. After, let's say, 2 seconds you call the Correction method. For example:

private int _ticks;

private void textBox1_TextChanged(object sender, EventArgs e)
{
    timer1.Start();
}

private void timer1_Tick(object sender, EventArgs e)
{
    if (_ticks++ == 4)
    {
        //Call correction method
        timer1.Stop();
        _ticks = 0;
    }
}

Answer 4

this is a silverlight user control i made (it's an extract from actual production code, works flawlessly) which does exactly what you need: react to input with a certain delay. it uses events to mimic "textchanged". Adapting it to windows forms is straightforward.

public partial class DelayedTextBox : UserControl
{
    private DispatcherTimer eventTimer = new DispatcherTimer();
    public double TextChangedDelay
    {
        get { return eventTimer.Interval.TotalMilliseconds; }
        set { eventTimer.Interval = TimeSpan.FromMilliseconds(value); }
    }

    public delegate void DelayedTextChangedHandler(object sender, RoutedEventArgs e);
    public event DelayedTextChangedHandler DelayedTextChange;

    private object relayedSender = null;
    private RoutedEventArgs relayedE = null;

    public string Text
    {
        get
        {
            return PlainTextBox.Text;
        }

        set
        {
            PlainTextBox.Text = string.IsNullOrEmpty(value) ? string.Empty : value;
        }
    }

    //----------------------------------------------------------------------------------------------
    public TimedTextChangedTextBox()
    {
        InitializeComponent();

        TextChangedDelay = 500;
        eventTimer.Tick += new EventHandler(eventTimer_Tick);
    }

    private void StartTimer(object sender, RoutedEventArgs e)
    {
        relayedSender = sender;
        relayedE = e;
        eventTimer.Start();
    }

    private void StopTimer()
    {
        eventTimer.Stop();
        relayedSender = null;
        relayedSender = null;
    }

    private void eventTimer_Tick(object sender, EventArgs e)
    {
        StopTimer();
        if (DelayedTextChange != null)
            DelayedTextChange(relayedSender, relayedE);
    }

    private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
    {
        if (!maskedInput)
            ReactToInput(sender, e);
    }

    private void ReactToInput(object sender, RoutedEventArgs e)
    {
        if (!eventTimer.IsEnabled)
        {
            StartTimer(sender, e);
        }
        else
        {
            StopTimer();
            StartTimer(sender, e);
        }
    }
}

you can use the control the exact same way you normally use a TextBox. subscribe to its DelayedTextChange event to react to user input.

Answer 5

This is obviously a really old post, but anyone looking for a simplified implementation may get some use out of the following:

using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

private Dictionary<string, string> AutoCorrectDictionary => 
    File.ReadAllLines(@"C:\AutoCorrect.txt").ToDictionary(ln => ln.Split('|')[0], ln => ln.Split('|')[1]);

private void textBox1_TextChanged(object sender, EventArgs e)
{
    var cur = textBox1.SelectionStart;
    var match = new Regex(@"[^\s]+\s$").Match(textBox1.Text.Substring(0, cur)).Value;
    if (!AutoCorrectDictionary.ContainsKey(match.Trim().ToLower())) return;
    var replaceTxt = $@"{AutoCorrectDictionary[match.Trim().ToLower()]} ";
    textBox1.Text = textBox1.Text.Remove(cur - match.Length, match.Length)
        .Insert(cur - match.Length, replaceTxt);
    textBox1.SelectionStart = cur + (replaceTxt.Length - match.Length);
}

The dictionary I used for this example ("C:\\AutoCorrect.txt") includes 970 entries of key/value pairs separated by a '|', but you could use whatever you like. In practice, I stick the AutoCorrectDictionary() in a static class that gets populated on startup. I did it the way I did here so that it would be clear what AutoCorrectDictionary() was.

Enjoy!