character entry restriction in the text book

Question

3.50/5 (2 votes)

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On the text box, it should allow the user to enter only 6 decimal places. Ex: 1.012345 or 1,012345
If 7 decimal places are tried, the entry should not be allowed.
Please refer the below code

C#

private void textBox1_KeyDown_1(object sender, KeyEventArgs e)
       {
           /// <summary>


           bool numericKeys = (
               (((e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9) ||
               (e.KeyCode >= Keys.NumPad0 && e.KeyCode <= Keys.NumPad9)) && e.Modifiers != Keys.Shift)
               || e.KeyCode == Keys.OemMinus
               || e.KeyCode == Keys.OemPeriod || e.KeyCode == Keys.Decimal || e.KeyCode == Keys.Oemcomma);

           bool navigationKeys = (
               e.KeyCode == Keys.Up ||
               e.KeyCode == Keys.Right ||
               e.KeyCode == Keys.Down ||
               e.KeyCode == Keys.Left ||
               e.KeyCode == Keys.Home ||
               e.KeyCode == Keys.End ||
               e.KeyCode == Keys.Tab);

           bool editKeys = (e.KeyCode == Keys.Delete ||
               e.KeyCode == Keys.Back);


           TextBox aTextbox = (TextBox)sender;
           aTextbox.Text = "2,33333";

           if (!string.IsNullOrEmpty(aTextbox.Text))
           {
               double maxIntensity;

               string aTextValue = aTextbox.Text;
               //convert it into the culture invariant type

               bool value = double.TryParse(aTextValue, NumberStyles.Any, CultureInfo.InvariantCulture.NumberFormat, out maxIntensity);

               if (value)
               {
                   string aText = maxIntensity.ToString();

                   MessageBox.Show("the value is {0}", aText);

                   string[] args = aText.Split('.');

                   if (numericKeys)
                   {
                       bool handleText = true;

                       if (args.Length > 2)
                       {
                           handleText = false;
                       }
                       else
                       {
                           if (args.Length == 2 && args[1] != null && args[1].Length > 5)
                           {
                               handleText = false;
                           }
                       }

                       if (!handleText)
                       {
                           e.SuppressKeyPress = true;
                           e.Handled = true;
                       }

                   }
               }
           }


           if (!(numericKeys || editKeys || navigationKeys))
           {
               e.SuppressKeyPress = true;
               e.Handled = true;
           }
       }
   }

Splitting the strings to seperate the real part and mantissa part (both are stored are strings), then I check the length of the mantissa part. If the length of the string is more than 5, I'd like to suppress the key.

Is there any other approach to do this?

Posted 13-Apr-11 0:50am

Raghav55

Updated 13-Apr-11 0:51am

Tarun.K.S

v2

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Comments

Pong D. Panda 13-Apr-11 7:02am

Does your code run? If not, what's the error?

Raghav55 13-Apr-11 7:04am

it works when the values is entered 23.333333
but when the values is entered as 23,333333
the entry is not restricted to 6 decimals places , user can enter more than 6 decimal places

Pong D. Panda 13-Apr-11 7:09am

Then that,s not an error, since the character ',' is considered as digit separator and not a decimal place separator.

Prerak Patel 13-Apr-11 7:26am

but in europian countries, ',' is decimal separator and '.' is digit separator. This may be the case.

Pong D. Panda 13-Apr-11 7:30am

Alright, but it seems that Prerak Patel already solved the mystery. Mark it as solved if it does.

2 solutions

Solution 1

> Is there any other approach to do this?
Yes. Use a MaskedTextBox or a NumericUpDown.
Both of them can be easily set up to match the expected behaviour.
Just use the properties Mask, respectively Decimals, i believe.

Posted 13-Apr-11 0:59am

Toli Cuturicu

Comments

Raghav55 13-Apr-11 7:00am

i have to use only normal text box

Toli Cuturicu 13-Apr-11 7:19am

No! You don't! A developer can use everything he wants.
But, if this is a homework, then we have a problem!
The question has to be tagged "homework", downvoted and / or deleted.
So, make up your mind.

Sergey Alexandrovich Kryukov 13-Apr-11 7:42am

You're absolutely right!
Some developers makes it practically offensive: answer my question but not say A and B.
This is the case. OP's relationships with the "boss" is not our concern.

Also, please read this:
http://www.codeproject.com/Messages/3854264/Re-QA.aspx

Chris makes a sensible point, don't he?

--SA

Sergey Alexandrovich Kryukov 13-Apr-11 7:39am

If you want to tell you know what to use, don't ask Questions!
--SA

Sergey Alexandrovich Kryukov 13-Apr-11 7:38am

Good point. My 5.
--SA

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

Prerak Patel · Accepted Answer · 2011-04-13T01:07:00

Solution 2

You can use RegEx as follows and modify it as per your need. You can easily convert it to C#[^]

VB

If Not isValid(TextBox1.Text) Then
  'block action here
End If

Function isValid(ByVal value As String) As Boolean
  Dim rex As New Regex("^\d+((\.|,)\d{0,6})?$")
  Return rex.Match(value).Success
End Function

[Edit]

C#

if (!isValid(TextBox1.Text)) {
        //block action here
}

public bool isValid(string value)
{
    Regex rex = new Regex("^\d+((\.|,)\d{0,6})?$");
    return rex.Match(value).Success;
}

Posted 13-Apr-11 1:07am

Prerak Patel

Updated 13-Apr-11 2:01am

v5

Comments

Toli Cuturicu 13-Apr-11 7:19am

What language is that?!

Pong D. Panda 13-Apr-11 7:23am

VB using regular expression

Toli Cuturicu 13-Apr-11 7:53am

Visual Basic?? The question is tagged c#!

Pong D. Panda 13-Apr-11 9:21am

You cant blame me. Im just answering his question based on his code above.

Prerak Patel 13-Apr-11 7:24am

It is call regular expressions. Google it to know more.

Toli Cuturicu 13-Apr-11 7:52am

I know regex. I don't know what Dim and ByVal means and in what language.
Anyway, I don't care. The question was clearly tagged c#.

Prerak Patel 13-Apr-11 7:55am

And that is why I have posted link to convert it to C#. Can't OP do atleast that on his own?!

Raghav55 13-Apr-11 7:59am

thanks , the solution works .But in one case it doesn't work, if the value .655555 is entered; the isvalid returns false.

Prerak Patel 13-Apr-11 8:02am

then use ^\d*((\.|,)\d{0,6})?$
I said, you can modify as per your need.

Raghav55 13-Apr-11 8:10am

thanks for the solution and moreover today i came to know that there are tools which convert code from one .net language to other language

character entry restriction in the text book

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character entry restriction in the text book

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