about good programming practice

Question

3.67/5 (3 votes)

See more:

VS2008

I have a question related to good programming practice.

Suppose I need to input a name of my customer in a text box, but the character to be input should only be letters and spaces. The customer can enter numbers, !@, etc, they can make an error unknowingly "arpan1" can be saved into the database.

There are two ways to solve this problem, one is when a user press save button then a message box can be displayed or error defining label can be shown as seen in many website forms, but what if we don't allow user to input numbers and other invalid characters. If the user presses 1 then the 1 or any other invalid character does not appear in the text box by some event handling method.

I would like to know which one is better to do?

Thank you,
Arpan

Posted 19-Nov-11 21:48pm

amsainju

Updated 19-Nov-11 22:46pm

André Kraak

v2

Add a Solution

Comments

Sergey Alexandrovich Kryukov 20-Nov-11 19:40pm

Good and important question; I voted 5; please see what I think about the matter.
--SA

3 solutions

Solution 1

you can do one thing, you can let a user to type what ever they want in the text box. later when before inserting the data into your database, just remove the charecters from the text box text.

Posted 19-Nov-11 21:55pm

Subhabrata Bose

Comments

amsainju 20-Nov-11 4:00am

will it be a good programming practice?

Sergey Alexandrovich Kryukov 20-Nov-11 19:27pm

It would be a very bad programming practice: unexpected, intrusive and confusing transformation of the user input. I would say: don't even play with similar ideas!
--SA

Albert Holguin 20-Nov-11 20:17pm

You can't just remove characters and pass the data on, the user has to be aware at all times that you're manipulating his input data.

Subhabrata Bose 20-Nov-11 23:54pm

what i have provided here is the simplest way. best way is to use validators for each text box.

Subhabrata Bose 21-Nov-11 0:02am

programming practice is not only protecting your data, but also good looking and user friendliness. so you can apply any way, link for validation: javascript function or asp validator control or custom validation from code behind.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-11-20T13:39:00

There is one simple principle: don't brainwash the user! Every time you show an extra error message to the user saying "What you just did is wrong, because you cannot use A, B and C" can be perceived as a brainwash.

Therefore, preventing such situation is much better. However, not in the way suggested by lion king — never do such things, just imagine the user emotion when she/he tried to type something and got something completely different. Even more reasonable "correct as you type" in text processor is switched off in many cases.

Your first bet would be filtering some useless characters. However, make sure you don't make process of typing more complex than that. Some developers try to make the filtering rules depending on the context, add some text, etc. This would be very confusing.

If the validity rules for the text are very complex, consider combination of filtering and validation. For example, you need to enter positive fractional number. You cannot really keep it valid while typing. Imagine the user typed a decimal separator (a point in English cultures) and later wanted to change its position. Imagine that you try to use a filter which would block an attempt to add more than one separator. A user can first delete one separator and type it again in another position; it will work. But a user could decide to type a second separator first and delete the first one after that. Blocking a second separator can confuse user too much. Therefore, you could just filter everything except digits, separator and possibly 'E' and '-', let the user type it and show the message "Invalid numeric format" or "… must be in the range…". Do it carefully and correctly. An exception handler can even set up a selection on a fragment of text to be fixed, but — never ever more that that! You don't want to be intrusive.

Good luck,

—SA

OriginalGriff · Accepted Answer · 2011-11-19T22:42:00

You can do this quite simply: just handle the TextBox.TextChanged event:

C#

char[] illegalCharacters = "!$%@.,".ToCharArray();
private void myTextBox_TextChanged(object sender, EventArgs e)
    {
    TextBox t = sender as TextBox;
    if (t != null)
        {
        string s = t.Text;
        int index = s.IndexOfAny(illegalCharacters);
        bool changed = false;
        int cpos = t.SelectionStart;
        while (index >= 0)
            {
            s = s.Remove(index, 1);
            changed = true;
            index = s.IndexOfAny(illegalCharacters);
            }
        if (changed)
            {
            t.Text = s;
            t.SelectionStart = cpos < s.Length ? cpos : s.Length;
            }
        }
    }

about good programming practice

3 solutions

Solution 3

Solution 2

Solution 1

Add your solution here

Preview 0