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I want to restrict my user to strictly input alphanumeric password only to open my application. Please provide c# code or algorithm for the same.
Posted 31-Jan-11 23:23pm
sk saini6.2K
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Solution 1

Register Textbox KeyPressEvent
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
// Allows only Alpha-Numeric’s
if (!(Char.IsLetter(e.KeyChar) || Char.IsDigit(e.KeyChar) || Char.IsControl (e.KeyChar)))
e.Handled = true;
sk saini at 1-Feb-11 6:45am
Thanks, its working.
shakil0304003 at 1-Feb-11 6:48am
Pravin Patil, Mumbai at 1-Feb-11 10:12am
Great solution shakil..
Simple but effective.
SAKryukov at 1-Feb-11 15:06pm
Correct; I voted "5". However the purpose is completely wrong, I think.
Please see my answer.
Marcus Kramer at 1-Feb-11 15:28pm
Agreed. +5 because the answer is 100% for the OP's question, but I too have serious questions about the theory behind doing this.
SAKryukov at 1-Feb-11 16:15pm
That's why I voted for Pravin's answer first.
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Solution 3

Refer Password Strength Control[^]

It has an excellent code to measure password strength.
I hope this helps.

All the best.
SAKryukov at 1-Feb-11 14:59pm
You're offering just the opposite to what OP wants; and I totally agree with you! - my 5.
I referenced your answer in mine -- please see.
Pravin Patil, Mumbai at 2-Feb-11 0:53am
Thanks SA.
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Solution 4

Just a note: what you want is considered as unsafe practice even in user's preferences. Look at any article on password strength. Pravin's answer is probably very adequate.

While other works tries to offer ways of encouraging users to create stronger passwords or, very typically, limits passwords to stronger ones by denying simple ones, you do exactly the opposite!

This is up to you, of course, but you're not helping your customers at all. It would be much, much, way to much better to allow them using any passwords at all.

Thank you for your understanding.

SAKryukov at 2-Feb-11 3:16am
I would say, this vote of "3" is a bright manifestation of stupidity, inability to understand a good advice, it it is contradict the preoccupation, no matter how wrong.
Sorry, for you, loser!
Manas Bhardwaj at 2-Feb-11 4:02am
+5 SA.
SAKryukov at 2-Feb-11 4:08am
Thank you, Manas.
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Solution 2

In the TextBox Event Select TextChainged Event And then place this code there
Note:-Replace Textbox Name Here
string charactersAllowed = "0123456789";
string theText = TEXTBOXNAME.Text;
string Letter = null;
int SelectionIndex = TEXTBOXNAME.SelectionStart;
int Change = 0;
for (int x = 0; x <= TEXTBOXNAME.Text.Length - 1; x++) {
    Letter = TEXTBOXNAME.Text.Substring(x, 1);
    if (charactersAllowed.Contains(Letter) == false) {
        theText = theText.Replace(Letter, string.Empty);
        Change = 1;
TEXTBOXNAME.Text = theText;
TEXTBOXNAME.Select(SelectionIndex - Change, 0);

CHECK OUT This it Realy Works.....
All the Best ....
sk saini at 1-Feb-11 6:24am
I applied this code but it doesn't accepts any letter in Textbox.
sk saini at 1-Feb-11 6:25am
Actually its taking input letter but simultaneously deleting the same.

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