Click here to Skip to main content
Click here to Skip to main content

VB.NET TextBox Validation Control

, 29 Apr 2005 CPOL
Rate this:
Please Sign up or sign in to vote.
A TextBox control witch validates user input with the use of a regular expression. If the user input is invalid, both foreground and background colors may be set to preset colors giving the user a visual clue. The control will also send an event to the hosting program when a validation error occurs.

The TextBoxValidate Demo


The TextBoxValidator control is a control that is inherited from the .NET Framework TextBox. This control will ensure that the information entered into the text box is valid for that field which it represents. The validation of the data is accomplished by sending the text value through the Regular Expression Match class. If the property Validation which holds the regular expression pattern is changed at run time, the the control will revalidate the data in the text box if it is not empty.

Using the code

To use the TextBoxValidate demo program, make sure both TextBoxValidateHost.exe and TextBoxValidate.dll are both in the same directory, and double click on the TextBoxValidateHost program. To install the control into your environment, open the Toolbox. Then select the tab you want the control to appear in, right click, and select “Add\Remove Items…”. When the “Customize Toolbox” window appears, select the “Browse…” button. When the “Open” dialog box appears, navigate to where you have placed the TextBoxValidate.dll and click the Open button. Then back in the “Customize Toolbox” window, click on the OK button. Now when you want to use the TextBoxValidator control, just drop it on a form and set the properties.

Toolbox icon

The icon displayed in the Toolbox window.

TextBoxValidate Properties

The properties added for the TextBoxValidator control.

The following four properties control the validation part of the control: ErrorBackColor and ErrorForeColor control the background and foreground colors of the text box when a validation error has occurred. Required is the property that will allow a field to be left blank (False) or must have a valid value (True) to be able to move on. The last property Validation is where the Regular Expression is placed to control the values allowed in the text box. You must be careful when entering a value for Validation so that what you want to validate is correctly defined by the regular expression. For example, if you want to validate a text field for a US phone number and selected the one Microsoft gives in the Regular Expression Editor, “((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}”, you will find that the expression will not only match (555) 555-1234 but also (555) 555-12345 and others. I used “^((\(\d{3}\) ?)\d{3}-\d{4})$|^(\d{3}-\d{3}-\d{4})$” in the demo program which matched a US phone number and nothing else, so please be careful. Also, if at run time the regular expression is modified, the control will validate the data in the text box if it contains any data.

Regular Expression Editor Showing Microsofts US Phone Number

Regular Expression Editor: You may type any regular expression in the Validation Expression text box shown above.

Look in the Microsoft documentation and the Web for information on regular expressions. The documents “Regular Expression Language Elements”, “Regular Expressions as a Language”, “.NET Framework Regular Expressions” and others can be found in the Microsoft documentation.

Revision History

  • April 12, 2005: Article first published.
  • April 23, 2005: Modified the code so that if the Validation pattern is changed at run time, it validates the data. A suggestion made by Oleg A. Lukin.


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


About the Author

Fernando Soto
Systems Engineer Unemployed
United States United States
No Biography provided

Comments and Discussions

AnswerRe: Toolbox icon? PinmemberMichael Ehrt12-Sep-05 2:02 
GeneralRe: Toolbox icon? PinmemberFernando Soto12-Sep-05 5:28 
GeneralRe: Toolbox icon? PinmemberFernando Soto12-Sep-05 5:31 
GeneralRe: Toolbox icon? PinmemberMichael Ehrt12-Sep-05 5:44 
Hi Fernando,
This line of code must have been added by the project conversion wizard in VS 2005 Beta 2 but not by me.
<ToolboxBitmap(GetType(TextBoxValidator), "TextBoxValidator.bmp")> _

No, I did it manually. This was what made it work for me.

If you go to the Solution Explorer window and right click on the image file TextBoxValidator.bmp that is in the TextBoxValidate project and select Properties from the floating menu you will see a property called “Build Action” and it should be set to “Embedded Resource”. This places the image into the dll itself and when loaded into the Toolbox the system will find the image resource and use it as the icon in the Toolbox.
yes, I noticed that in your example code. Still, the image didn't show up untill I manually set the class attribute using the code line above. Probably Beta 2 behaves a little differently than previous versions, intended or not...
Also, I actually prefer to set the bitmap reference manually, because you can of course compile one DLL file containing multiple control classes. And if it were done in some automatic way as your posting suggests - if you have a dll containing two control classes with two images, in which way would they be joined together? By name...?

-- modified at 10:44 Monday 12th September, 2005
GeneralRe: Toolbox icon? PinmemberFernando Soto12-Sep-05 6:35 
AnswerRe: Toolbox icon? PinmemberFernando Soto12-Sep-05 5:08 
GeneralDear Fernando: about .net version supported Pinsussdundask11-Sep-05 1:45 
GeneralRe: Dear Fernando: about .net version supported PinmemberFernando Soto11-Sep-05 7:27 
GeneralRe: Dear Fernando: about .net version supported Pinmemberdundask12-Sep-05 7:33 
GeneralRe: Dear Fernando: about .net version supported PinmemberFernando Soto12-Sep-05 7:47 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web02 | 2.8.150301.1 | Last Updated 29 Apr 2005
Article Copyright 2005 by Fernando Soto
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid