Alphanumeric character validation in C#

[kanepart2]

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Some help would be appreciated

 

[Mahmoud Al-Qudsi]

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Some help would be appreciated

try isDigit and isChar functions when validating the .keydown action.

 

[Daniel Cigic]

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Some help would be appreciated

This is not complete but something like this I gues:

You can add KeyDown event handler to your textbox ... for example:

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
if(e.KeyCode == Keys.OemMinus) // and of course more checks
here ....
{
e.SuppressKeyPress = true;
e.Handled = true;
}
}

 

[BLUE]

//
// AlphaNumTextBox.cs
//

using System;
using System.Windows.Forms;

namespace AlphaNumericTextBox
{
/// <remarks>
/// A text box to contain alphanumeric data
/// </remarks>
internal sealed class AlphaNumTextBox : TextBox
{
#region Fields

private bool isBack = false;
private bool isAlphaNum = false;

#endregion

#region Event raisers

protected override void OnKeyDown(KeyEventArgs e)
{
Keys k = e.KeyCode;

if (k == Keys.Back)
{
this.isBack = true;
this.isAlphaNum = false;
}
else
{
bool isAlpha = !e.Alt && !e.Control && (k >= Keys.A && k <=
Keys.Z);

// Determine whether the keystroke is a number
bool d0d9 = k >= Keys.D0 && k <= Keys.D9;
bool numpad = k >= Keys.NumPad0 && k <= Keys.NumPad9;
bool isNumber = (!e.Alt && !e.Control && !e.Shift) && (d0d9
|| numpad);

this.isBack = false;
this.isAlphaNum = isAlpha || isNumber;
}
base.OnKeyDown(e);
}

protected override void OnKeyPress(KeyPressEventArgs e)
{
if (!this.isBack && !this.isAlphaNum)
{
e.Handled = true;
return;
}

char c = e.KeyChar;

if (this.isBack && this.SelectionStart > 0)
{
int currentPosition = SelectionStart;
this.Text = this.Text.Substring(0, this.TextLength - 1);
this.SelectionStart = currentPosition - 1;
e.Handled = true;
return;
}

if (this.isAlphaNum && this.SelectionStart < this.MaxLength)
{
int currentPosition = SelectionStart;
this.Text = this.Text.Insert(currentPosition,
Char.ToUpper(c).ToString());
this.SelectionStart = currentPosition + 1;
e.Handled = true;
return;
}

base.OnKeyPress(e);
}

#endregion
}
}


Bye,
Luigi.

 

[kanepart2]

I tried both the above . e does not have a property called KeyCode

 

[Morten Wennevik [C# MVP]]

try isDigit and isChar functions when validating the .keydown action.

Even better,

Char.IsLetterOrDigit(char), you need to use the KeyPress event to get the characters and cancel (Handled) the event.

 

[Peter Duniho]

I tried both the above . e does not have a property called KeyCode

Sure it does, if you are actually handling the KeyDown event which has the
KeyEventArgs parameter:

http://msdn2.microsoft.com/en-us/library/system.windows.forms.keyeventargs.keycode.aspx

That said, it seems to me that Morton's advice about using the KeyPress
event instead is better. Set the e.Handled property to "true" to avoid
non-alphanumeric characters from being entered.

Also note that there's a MaskedTextBox that will do this sort of filtering
for you. If all you are trying to do is restrict input to alphanumerics,
that might be a better choice.

Pete

 

[Mihai N.]

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Filtering at key-press is usually the bad approach.
It will mess-up a languages that have more complex input
(dead-keys, IME, etc.)

 

[Pallavi Gajane]

Can we use this c# code to encrypt alphanumeric plaintext in RSA algorithm?

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Some help would be appreciated

On Wednesday, May 30, 2007 1:31 PM Mahmoud Al-Qudsi wrote:
try isDigit and isChar functions when validating the .keydown action.

On Wednesday, May 30, 2007 1:59 PM Morten Wennevik [C# MVP] wrote:
Even better,

Char.IsLetterOrDigit(char), you need to use the KeyPress event to get the characters and cancel (Handled) the event.

 

[Pallavi Gajane]

Can we use alphanumeric plaintext in c# using RSA algorithm?

Hey all,

I have to validate a textbox in windows forms for alphanumeric
characters such that non alphanumeric key presses are ignored.

Some help would be appreciated

On Wednesday, May 30, 2007 1:31 PM Mahmoud Al-Qudsi wrote:
try isDigit and isChar functions when validating the .keydown action.

On Wednesday, May 30, 2007 1:59 PM Morten Wennevik [C# MVP] wrote:
Even better,

Char.IsLetterOrDigit(char), you need to use the KeyPress event to get the characters and cancel (Handled) the event.