Allow only string values in xaml.cs

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I want to allow user to only enter string values in textbox but my code is not working well

C#

string allowedCharacterSet = "bcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\b\n\t";

        if (allowedCharacterSet.Contains(e.Key.ToString() ))
        {

        }
        else
        {
            e.Handled = true;
        }

Posted 29-May-13 9:46am

Zain ul abdeen

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Richard C Bishop 29-May-13 16:01pm

You are completely confused on what you are attempting to do. No worries, it is simple to accomplish this task. Simply use a reg ex to only allow alpha characters.

Sergey Alexandrovich Kryukov 29-May-13 17:12pm

Formally, the request makes no sense. Please see the first line of my answer.

However, if you remove one sloppy word from the post, it does make some sense, and I think finding out the implementation is not that trivial, for a beginner.
Therefore, please see the rest of my answer.

—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-05-29T11:11:00

It is already totally impossible for a user to enter anything except a string value. Case closed.

However, if you want to allow only certain characters from your user input, and if you are talking about some text box, you should handle the event System.Windows.Controls.Primitives.TextBoxBase.TextChanged:
http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.textboxbase.textchanged.aspx[^].

With this event, you have the opportunity to cancel the change. Please see:
http://msdn.microsoft.com/en-us/library/system.windows.controls.textchangedeventhandler.aspx[^],
http://msdn.microsoft.com/en-us/library/system.windows.controls.textchangedeventargs.aspx[^].

Here is how: you need to assign the property System.Windows.Controls.TextChangedEventArgs.Handled to true:
http://msdn.microsoft.com/en-us/library/system.windows.routedeventargs.handled.aspx[^].

You are about to make one more mistake: to filter out backspace, which is, by some historical reasons, is considered as a character. Its code point is 8. Allow it, too.

Good luck,

—SA