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Numeric TextBox

, 1 Apr 2006
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The article disucusses a new way to let a TextBox only accept numeric values, without using custom controls.

Sample Image - NumericTextBox.gif


Many of us have faced a situation where we want the user to enter a number (an integer or a double) in a TextBox, thus seeking a way to prevent him from inserting invalid characters. Almost all of the available solutions required to use a custom control inherited from TextBox control. Regarding the fact that the developers sometimes (or perhaps often!) decide to add this facility to their TextBoxes after they have added several TextBox controls, and added many other lines of code to their project based on these controls names, these solutions are practically of limited use. (The programmer needs to remove all TextBoxes, add the new custom control instead of each of them, and make all the required changes to the code.)

Considering that, I broke the project to two blocks:

  1. To validate each character a user presses on the keyboard, check if its addition to the current value of the TextBox will still result in a numeric value, and prevent the character to be added to the TextBox value if the answer is no.
  2. To perform the validation on pasting into the TextBox. Pasting could be done through pressing CTRL+V, SHIFT+INSERT or using the right-click context menu.

The first issue can be handled using the onKeyPress event of the TextBox. For the second part, unfortunately, we don't have an onPaste event. I used a brilliant method dedicated in this Experts-Exchange thread.

Using the code

You will need to set the numericTextboxKeyPress sub to handle the onKeyPress event for all TextBoxes you want to validate. This will handle the input characters as the user types them.

The creative TextBoxOnChange class handles the paste event for the TextBoxes. For each TextBox on which you want to handle the paste event, you should add a line of code like this:

//Example of adding an onPaste handler
Dim onPaste1 As New TextBoxOnPaste(Me.TextBox1)

I added two checkboxes to the demo project source code to facilitate your learning how to use the code for multiple checkboxes.


25 Feb 2006 : Minor bug fixes.

19 Feb 2006 : Original article submitted.


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About the Author

Hojjat Salmasian
Web Developer
United States United States
No Biography provided

Comments and Discussions

QuestionNumeric TextBox in VB.Net PinmemberSumitSaha11-Jan-15 16:42 
GeneralMy vote of 5 PinmemberPawan.riseup3-Jun-14 23:34 
GeneralMy vote of 1 PinmemberKazna4ey8-Jun-13 7:51 
QuestionAdvanced Numeric PinmemberSureshjv11-Dec-12 20:54 
QuestionHey You can check here Advanced Numeric Text Box PinmemberSureshjv11-Dec-12 20:53 
GeneralPasted data Pinmemberiamthecodecutter8-May-11 20:26 
GeneralMy vote of 1 Pinmembersaeed mousavi4-Feb-09 5:54 
GeneralCool and what about positive numbers PinmemberSalarSoft11-Jul-07 21:07 
Generaldecimal point Pinmembertorbero11-Jul-07 9:30 
Is your code very useful, but is it necessary to control that alone a decimal point is introduced 23.3443 and not 23.34.43 like one can make it?

GeneralRe: decimal point PinmemberHojjat Salmasian12-Jul-07 5:16 
GeneralSmall Issue PinmemberMNC6217-Jun-07 22:26 
GeneralFlaw.... Pinmemberchris1759-Feb-07 8:31 
GeneralRe: Flaw.... PinmemberHojjat Salmasian9-Feb-07 10:58 
GeneralThank you PinmemberPocketJem5-Dec-06 10:49 
GeneralRe: Thank you PinmemberHojjat Salmasian5-Dec-06 20:06 
GeneralRe: Thank you PinmemberPocketJem6-Dec-06 9:35 
GeneralRe: Thank you PinmemberHojjat Salmasian7-Dec-06 7:58 
GeneralThe contorl don't support inputing minus symbol. Pinmemberzxp31922-Feb-06 21:46 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberHojjat Salmasian23-Feb-06 5:35 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberRay Cassick25-Feb-06 12:22 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberHojjat Salmasian26-Feb-06 7:31 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberRay Cassick26-Feb-06 8:12 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberHojjat Salmasian27-Feb-06 7:46 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberLovinBill13-Jul-06 0:56 
GeneralRe: The contorl don't support inputing minus symbol. PinmemberHojjat Salmasian15-Jul-06 5:06 

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