Validation-Textboxes allowing only decimals

I am using following code for validating textbox.

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    e.Handled = SingleDecimal(sender, e.KeyChar);
}

public bool SingleDecimal(System.Object sender, char eChar)
{
    string chkstr = "0123456789.";
    if (chkstr.IndexOf(eChar) > -1 || eChar == Constants.vbBack) 
    {
        if (eChar == ".") 
        {
            if (((TextBox)sender).Text.IndexOf(eChar) > -1) 
            {     
    开发者_如何学JAVA            return true;
            }
            else 
            {         
                return false;  
            }
        }   
        return false;
     }
     else 
     {
         return true;  
     }
}

Problem is Constants.vbBack is showing error.If i didnt use Constants.vbBack,backspace is not workimg.What alteration can i make to work backspace.Can anybody help?

here is the code I would use...

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    // allows 0-9, backspace, and decimal
    if (((e.KeyChar < 48 || e.KeyChar > 57) && e.KeyChar != 8 && e.KeyChar != 46))
    {
        e.Handled = true;
        return;
    }

    // checks to make sure only 1 decimal is allowed
    if (e.KeyChar == 46)
    {
        if ((sender as TextBox).Text.IndexOf(e.KeyChar) != -1)
            e.Handled = true;
    }
}

You can make a method to check if it's a number.

Instead of checking for the . as a decimal separator you should get it from CurrentCulture object as it could be another character depending on where in the world you are.

public bool isNumber(char ch, string text)
{
    bool res = true;
    char decimalChar = Convert.ToChar(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);

    //check if it´s a decimal separator and if doesn´t already have one in the text string
    if (ch == decimalChar && text.IndexOf(decimalChar) != -1)
    {
        res = false;
        return res;
    }

    //check if it´s a digit, decimal separator and backspace
    if (!Char.IsDigit(ch) && ch != decimalChar && ch != (char)Keys.Back)
        res = false;

    return res;
}

Then you can call the method in the KeyPress event of the TextBox:

private void TextBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if(!isNumber(e.KeyChar,TextBox1.Text))
        e.Handled=true;
}

create a component inherited from textbox and use this code:

    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && e.KeyChar != '.')
        {
            e.Handled = true;
        }

        // only allow one decimal point
        if (e.KeyChar == '.' && Text.IndexOf('.') > -1)
        {
            e.Handled = true;
        }

        base.OnKeyPress(e);
    }

Here is a Vb.Net version for @Eclipsed4utoo's answer

If (((Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57) And Asc(e.KeyChar) <> 8 And Asc(e.KeyChar) <> 46)) Then
    e.Handled = True
    Exit Sub
End If

' checks to make sure only 1 decimal is allowed
If (Asc(e.KeyChar) = 46) Then
    If (sender.Text.IndexOf(e.KeyChar) <> -1) Then
        e.Handled = True
    End If
End If

This codes for decimals. If you want to use float also, you just use double insteat int And it will be delete automaticaly last wrong charachters

private void txt_miktar_TextChanged(object sender, TextChangedEventArgs e)
    {
        if ((sender as TextBox).Text.Length < 1)
        {
            return;
        }

        try
        {
            int adet = Convert.ToInt32((sender as TextBox).Text);
        }
        catch
        {
            string s = "";
            s = (sender as TextBox).Text;
            s = s.Substring(0, s.Length - 1);
            (sender as TextBox).Text = s;
            (sender as TextBox).Select(s.Length, s.Length);
        }
    }

How about using the example from MSDN?

Are u using the '.' as decimal seperator? if so than I don't know why you are using

if (((TextBox)sender).Text.IndexOf(eChar) > -1)

Here some code from my app. It handle one more case as will related to selection

protected override void OnKeyPress(KeyPressEventArgs e)
{
    if (e.KeyChar == '\b')
        return;
    string newStr;
    if (SelectionLength > 0)
        newStr = Text.Remove(SelectionStart, SelectionLength);

    newStr = Text.Insert(SelectionStart, new string(e.KeyChar, 1));
    double v;
   //I used regular expression but you can use following.
    e.Handled = !double.TryParse(newStr,out v);

    base.OnKeyPress(e);
}

here regex expression if like to use them instead of that easy type parsing

const string SIGNED_FLOAT_KEY_REGX = @"^[+-]?[0-9]*(\.[0-9]*)?([Ee][+-]?[0-9]*)?$";
const string SIGNED_INTEGER_KEY_REGX = @"^[+-]?[0-9]*$";

const string SIGNED_FLOAT_REGX = @"^[+-]?[0-9]*(\.[0-9]+)?([Ee][+-]?[0-9]+)?$";
const string SIGNED_INTEGER_REGX = @"^[+-]?[0-9]+$";

I believe this is the perfect solution as it not only confines the text to numbers, only a leading minus sign, and only one decimal point, but it allows the replacement of selected text if it contains a decimal point. The selected text still cannot be replaced by a decimal point if there is a decimal point in the non-selected text. It allows a minus sign only if it's the first character or if the entire text is selected.

private bool DecimalOnly_KeyPress(TextBox txt, bool numeric, KeyPressEventArgs e)
{
  if (numeric)
  {
    // only allow numbers
    if (!char.IsDigit(e.KeyChar) && e.KeyChar != Convert.ToChar(Keys.Back))     
      return true;
  }
  else
  {
    // allow a minus sign if it's the first character or the entire text is selected
    if (e.KeyChar == '-' && (txt.Text == "" || txt.SelectedText == txt.Text))
      return false;

    // if a decimal point is entered and if one is not already in the string
    if ((e.KeyChar == '.') && (txt.Text.IndexOf('.') > -1))                     
    {
      if (txt.SelectedText.IndexOf('.') > -1)
        // allow a decimal point if the selected text contains a decimal point, that is the
        // decimal point replaces the selected text 
        return false;
      else
        // don't allow a decimal point if one is already in the string and the selected text
        // doesn't contain one
        return true;                                                        
    }

    // if the entry is not a digit
    if (!Char.IsDigit(e.KeyChar))                                               
    {
      // if it's not a decimal point and it's not a backspace then disallow
      if ((e.KeyChar != '.') && (e.KeyChar != Convert.ToChar(Keys.Back)))     
      {
        return true;
      }
    }
  }

  // allow only a minus sign but only in the beginning, only one decimal point, any digit, a
  // backspace, and replace selected text.
  return false;                                                                   
}

Here is a vb.net version that allows negative decimal figure, prevent copy and paste while making sure the negative sign is not in the middle of the text or the decimal point not at the beginning of the text

Public Sub Numeric(textControl As Object, e As KeyPressEventArgs)

    Dim Index As Int32 = textControl.SelectionStart
    Dim currentLine As Int32 = textControl.GetLineFromCharIndex(Index)
    Dim currentColumn As Int32 = Index - textControl.GetFirstCharIndexFromLine(currentLine)

    Dim FullStop As Char
    FullStop = "."

    Dim Neg As Char
    Neg = "-"

    ' if the '.' key was pressed see if there already is a '.' in the string
    ' if so, dont handle the keypress
    If e.KeyChar = FullStop And textControl.Text.IndexOf(FullStop) <> -1 Then
        e.Handled = True
        Return
    End If
    'If the '.' is at the begining of the figures, prevent it
    If e.KeyChar = FullStop And currentColumn <= 0 Then
        e.Handled = True
        Return
    End If

    ' if the '-' key was pressed see if there already is a '-' in the string
    ' if so, dont handle the keypress

    If e.KeyChar = Neg And textControl.Text.IndexOf(Neg) <> -1 Then
        e.Handled = True
        Return
    End If
    'If the '-' is in the middle of the figures, prevent it
    If e.KeyChar = Neg And currentColumn > 0 Then
        e.Handled = True
        Return
    End If

    ' If the key aint a digit
    If Not Char.IsDigit(e.KeyChar) Then
        ' verify whether special keys were pressed
        ' (i.e. all allowed non digit keys - in this example
        ' only space and the '.' are validated)
        If (e.KeyChar <> Neg) And (e.KeyChar <> FullStop) And (e.KeyChar <> Convert.ToChar(Keys.Back)) Then
            ' if its a non-allowed key, dont handle the keypress
            e.Handled = True
            Return
        End If
    End If

End Sub



Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress

        Numeric(sender, e)

End Sub

try this with asp:RegularExpressionValidator controller

<asp:RegularExpressionValidator ID="rgx" 
ValidationExpression="[0-9]*\.?[0-9][0-9]" ControlToValidate="YourTextBox" runat="server" ForeColor="Red" ErrorMessage="Decimals only!!" Display="Dynamic"  ValidationGroup="lnkSave"></asp:RegularExpressionValidator>