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Prevent continue Typing in TextBox When a Char is Entered

I have a textbox which user should type a price in it.
I need to prevent continue typing if price starts with 0.
For example user can not type "000" or "00009".
I tried this on KeyPress, but nothing!
if (txt.Text.StartsWith("0"))
return; Or e.Handeled = true;

try this:
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
//only allow digit and (.) and backspace
if ((e.KeyChar < '0' || e.KeyChar > '9') && e.KeyChar != '\b' && e.KeyChar != '.')
{
e.Handled = true;
}
var txt = sender as TextBox;
//only allow one dot
if (txt.Text.Contains('.') && e.KeyChar == (int)'.')
{
e.Handled = true;
}
//if 0, only allow 0.xxxx
if (txt.Text.StartsWith("0")
&& !txt.Text.StartsWith("0.")
&& e.KeyChar != '\b'
&& e.KeyChar != (int)'.')
{
e.Handled = true;
}
}

You could use the TextChanged-event for this.
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (this.textBox1.Text == "0") this.textBox1.Text = "";
}
This will only work, if the TextBox is empty on startup.

I solved it Myself:
private void txtPrice_KeyPress(object sender, KeyPressEventArgs e)
{
if (txtPrice.Text.StartsWith("0") && !char.IsControl(e.KeyChar))
{
e.Handled = true;
return;
}
}

KeyPress Event gives wrong value

I made a KeyPress Event and want to allow only Double values (or just digits and comma) so I tried this:
e.Handled = !(char.IsNumber(e.KeyChar) || e.KeyChar == (char)Keys.Back || e.KeyChar == (char)Keys.Decimal);
But somehow he's got problems with the "Decimal". I'm using a german keyboard and when I try to enter the comma, he does nothing. When I press the "n" key he writes the letter. What is wrong here and how to solve that?

you can restrict the input using keyPress event like so:
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char c= e.KeyChar;
if (!char.IsDigit(c) && !char.IsControl(c))
{
e.Handled = true;
}
}
if we want to extend our restriction condition to accept a certain character (for example ,)
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char c= e.KeyChar;
if (!char.IsDigit(c) && !char.IsControl(c) && c!=',')
{
e.Handled = true;
}
}
To avoid having multiple comma like 222,34545,454 we can do this work around:
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char c= e.KeyChar;
bool comma= textBox1.Text.Contains(','); //true in case comma already inserted
// accepts only digits, controls and comma
if (!char.IsDigit(c) && !char.IsControl(c) && c!=',')
{
e.Handled = true;
return;
}
// whenever a comma is inserted we check if we already have one
if (c == ',' && comma)
{
e.Handled = true;
}
}

can't determine '.' keychar for a textbox KeyPress event

I use below code to not allowing any character except numbers in a textbox ... but it allows '.' character! I don't want it to allow dot.
private void txtJustNumber_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsDigit((char)(e.KeyChar)) &&
e.KeyChar != ((char)(Keys.Enter)) &&
e.KeyChar != (char)(Keys.Delete) &&
e.KeyChar != (char)(Keys.Back)&&
e.KeyChar !=(char)(Keys.OemPeriod))
{
e.Handled = true;
}
}

use this:
if (!char.IsDigit((char)(e.KeyChar)) &&
e.KeyChar != ((char)(Keys.Enter)) &&
(e.KeyChar != (char)(Keys.Delete) || e.KeyChar == Char.Parse(".")) &&
e.KeyChar != (char)(Keys.Back)
)
it is because Keys.Delete's char value is 46 which is the same as '.'. I do not know why it likes this.

You could try this instead (where textBox1 would be your textbox):
// Hook up the text changed event.
textBox1.TextChanged += textBox1_TextChanged;
...
private void textBox1_TextChanged(object sender, EventArgs e)
{
// Replace all non-digit char's with empty string.
textBox1.Text = Regex.Replace(textBox1.Text, #"[^\d]", "");
}
Or
// Save the regular expression object globally (so it won't be created every time the text is changed).
Regex reg = new Regex(#"[^\d]");
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (reg.IsMatch(textBox1.Text))
textBox1.Text = reg.Replace(textBox1.Text, ""); // Replace only if it matches.
}

//This is the shortest way
private void txtJustNumber_KeyPress(object sender, KeyPressEventArgs e)
{
if(!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}

try this code for your problem in keypress event :
private void txtMazaneh_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsDigit(e.KeyChar) && (int)e.KeyChar != 8 ||(e.KeyChar= .))
e.Handled = true;
}

textbox display formatting with decimal point

I want to add "," after every group of 3 digits. Eg : when I type 123456789 the textbox will display 123,456,789 and I got it with this code:
private void textBox1_KeyUp(object sender, KeyEventArgs e)
{
if (!string.IsNullOrEmpty(textBox1.Text))
{
System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo("en-US");
decimal valueBefore = decimal.Parse(textBox1.Text, System.Globalization.NumberStyles.AllowThousands);
textBox1.Text = String.Format(culture, "{0:N0}", valueBefore);
textBox1.Select(textBox1.Text.Length, 0);
}
}
I want to be more specific for this format. I want to type numeric only for this textbox and use decimal format (type . after that) like 123,456,789.00 and I try to use this code:
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && e.KeyChar != '.')
{
e.Handled = true;
}
}
but it doesn't work

You can use digit grouping format string as defined in MSDN
Something like following should work (modified version):
private void textBox1_TextChanged(object sender, EventArgs e)
{
decimal myValue;
if (decimal.TryParse(textBox1.Text, out myValue))
{
textBox1.Text = myValue.ToString("N", CultureInfo.CreateSpecificCulture("en-US"));
textBox1.SelectionStart = 0;
textBox1.SelectionLength = 0;
}
}
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsDigit(e.KeyChar) && e.KeyChar != '.')
{
e.Handled = true;
}
}

http://msdn.microsoft.com/en-us/library/fzeeb5cd.aspx#Y600
After you have parsed the value into the decimal data type, just assign textbox1.Text the value of that decimal variable using ToString, and passing it a format parameter.
TextBox1.Text = valueBefore.ToString("C")
As far as preventing the input to the textbox, I thought for sure there was a mode for that already.
Anyway, try this:
if !(Char.IsControl(e.KeyChar) || Char.IsDigit(e.KeyChar) || (e.KeyChar == Keys.Decimal && !(TextBox1.Text.Contains("."))))
{
e.Handled = true;
}

How to make a TextBox accept only alphabetic characters?

How can I make a TextBox only accept alphabetic characters with spaces?

You could use the following snippet:
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (!System.Text.RegularExpressions.Regex.IsMatch(textBox1.Text, "^[a-zA-Z ]"))
{
MessageBox.Show("This textbox accepts only alphabetical characters");
textBox1.Text.Remove(textBox1.Text.Length - 1);
}
}

You can try by handling the KeyPress event for the textbox
void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back);
}
Additionally say allow backspace in case you want to remove some text, this should work perfectly fine for you
EDIT
The above code won't work for paste in the field for which i believe you will have to use TextChanged event but then it would be a bit more complicated with you having to remove the incorrect char or highlight it and place the cursor for the user to make the correction Or maybe you could validate once the user has entered the complete text and tabs off the control.

private void textbox1_KeyDown_1(object sender, KeyEventArgs e)
{
if (e.Key >= Key.A && e.Key <= Key.Z)
{
}
else
{
e.Handled = true;
}
}

The simplest way is to handle the TextChangedEvent and check what's been typed:
string oldText = string.Empty;
private void textBox2_TextChanged(object sender, EventArgs e)
{
if (textBox2.Text.All(chr => char.IsLetter(chr)))
{
oldText = textBox2.Text;
textBox2.Text = oldText;
textBox2.BackColor = System.Drawing.Color.White;
textBox2.ForeColor = System.Drawing.Color.Black;
}
else
{
textBox2.Text = oldText;
textBox2.BackColor = System.Drawing.Color.Red;
textBox2.ForeColor = System.Drawing.Color.White;
}
textBox2.SelectionStart = textBox2.Text.Length;
}
This is a regex-free version if you prefer. It will make the text box blink on bad input.
Please note that it also seems to support paste operations as well.

Write Code in Text_KeyPress Event as
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsLetter(e.KeyChar))
{
e.Handled = true;
}
}

This one is working absolutely fine...
private void manufacturerOrSupplierTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
if (char.IsControl(e.KeyChar) || char.IsLetter(e.KeyChar))
{
return;
}
e.Handled = true;
}

This solution uses regular expressions, does not allow invalid characters to be pasted into the text box and maintains the cursor position.
using System.Text.RegularExpressions;
int CursorWas;
string WhatItWas;
private void textBox1_Enter(object sender, EventArgs e)
{
WhatItWas = textBox1.Text;
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (Regex.IsMatch(textBox1.Text, "^[a-zA-Z ]*$"))
{
WhatItWas = textBox1.Text;
}
else
{
CursorWas = textBox1.SelectionStart == 0 ? 0 : textBox1.SelectionStart - 1;
textBox1.Text = WhatItWas;
textBox1.SelectionStart = CursorWas;
}
}
Note: textBox1_TextChanged recursive call.

if (System.Text.RegularExpressions.Regex.IsMatch(textBox1.Text, "^[a-zA-Z]+$"))
{
}
else
{
textBox1.Text = textBox1.Text.Remove(textBox1.Text.Length - 1);
MessageBox.Show("Enter only Alphabets");
}
Please Try this

private void textBox2_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar >= '0' && e.KeyChar <= '9')
e.Handled = true;
else
e.Handled = false;
}

Try This
private void tbCustomerName_KeyPress(object sender, KeyPressEventArgs e)
{
e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back||e.KeyChar==(char)Keys.Space);
}
It Allows White Spaces Too

you can try following code that alert at the time of key press event
private void tbOwnerName_KeyPress(object sender, KeyPressEventArgs e)
{
//===================to accept only charactrs & space/backspace=============================================
if (e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back || e.KeyChar == (char)Keys.Space))
{
e.Handled = true;
base.OnKeyPress(e);
MessageBox.Show("enter characters only");
}

Here is my solution and it works as planned:
string errmsg = "ERROR : Wrong input";
ErrorLbl.Text = errmsg;
if (e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back || e.KeyChar == (char)Keys.Space))
{
ErrorLbl.Text = "ERROR : Wrong input";
}
else ErrorLbl.Text = string.Empty;
if (ErrorLbl.Text == errmsg)
{
Nametxt.Text = string.Empty;
}

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsControl(e.KeyChar) && !char.IsLetter(e.KeyChar) &&
(e.KeyChar !='.'))
{
e.Handled = true;
MessageBox.Show("Only Alphabets");
}
}

Try following code in KeyPress event of textbox
if (char.IsLetter(e.KeyChar) == false &
Convert.ToString(e.KeyChar) != Microsoft.VisualBasic.Constants.vbBack)
e.Handled = true

works for me, even though not the simplest one.
private void Alpha_Click(object sender, EventArgs e)
{
int count = 0;
foreach (char letter in inputTXT.Text)
{
if (Char.IsLetter(letter))
{
count++;
}
else
{
count = 0;
}
}
if (count != inputTXT.Text.Length)
{
errorBox.Text = "The input text must contain only alphabetic characters";
}
else
{
errorBox.Text = "";
}
}

This works fine as far as characters restriction, Any suggestions on error msg prompt with my code if it's not C OR L
Private Sub TXTBOX_TextChanged(sender As System.Object, e As System.EventArgs) Handles TXTBOX.TextChanged
Dim allowed As String = "C,L"
For Each C As Char In TXTBOX.Text
If allowed.Contains(C) = False Then
TXTBOX.Text = TXTBOX.Text.Remove(TXTBOX.SelectionStart - 1, 1)
TXTBOX.Select(TXTBOX.Text.Count, 0)
End If
Next
End Sub

Try this one. Spaces and shortcut keys work
if (!char.IsControl(e.KeyChar) && !char.IsLetter(e.KeyChar) && !char.IsSeparator(e.KeyChar))
{
e.Handled = true;
}