Validators for Windows Forms - ValidationProvider Control

• Download source files - 107 Kb
• Download demo project - 30.7 Kb

Introduction

Do you spend most of your time writing custom validations on Windows Forms? Have you ever wanted an equivalent WinForm validator like in WebForm? Noogen ValidationProvider can help you speed up your WinForms design time by providing powerful, easy and virtually code-free wiring of input validations.

Background

For the beginners, I would suggest a reading of Paul Riley's article on Validators in ASP.NET/WebForms - ASP.NET Validators Unclouded. This is because ValidationProvider engine is derived from WebForm Validators base.

Noogen ValidationProvider is also built on ErrorProvider, see the article by Naveen K. Kohli - How To Use The ErrorProvider Object To Indicate Invalid Control State.

I know that this topic has been discussed many times (example MSDN article - Extending Windows Forms with a Custom Validation Component Library, Part 3), but most of the articles I've seen are either too restricted to a single control (TextBox) or too complicated. My goal with Noogen ValidationProvider is to bring all these great ideas together and simplify them.

The design

1. To speed up development, Noogen ValidationProvider re-uses WebForm validator base engine and displays error using ErrorProvider Control (hence the name ValidationProvider).
2. My second goal is to provide easy wiring of basic/familiar validations as seen in WebForm, which includes: DataTypes check, required field, range and value comparison validations, and more...
3. Noogen ValidationProvider also tests and validates regular expressions and can even wire more advance custom validations.

I'll stop here before I go too far off from the topic. Of course, if you wish to drill down on the details, all the source codes are provided.

Using the code

Basic Validations

ValidationProvider makes it easy to setup validation for TextBox and ComboBox controls. You don't have to write a single line of code. Just compile the accompanied source in release mode, browse and add it to your VS.NET IDE ToolBox, drop it on the form, and you are ready to visually design your input validations.

ValidationProvider property exposes Edit ValidationRules link/verb on the "Properties Window". I have also implemented IExtenderProvider to enable easy editing of specific ValidationRule ties to individual TextBox or ComboBox controls.

The only code you will need is given below:

//
// Call Noogen ValidationProvider public method - 
// Validate() and display error if returns false.
//
this.validationProvider1.ValidationMessages(
                      !this.validationProvider1.Validate());

Public Methods

Regular expression validations

ValidationProvider can test and validate regular expressions (RegEx). For your convenience, a RegEx test bench is provided. RegEx test value applies the same validation engine, and the data gets validated as you type in. You can wire some very powerful and advance validations with RegEx. With creativity, I believe that you can virtually use it in place of all the Basic Validations, but RegEx can be complicated to derive. Thus, you would probably use RegEx validation as an accommodation to the provided Basic Validations. The demo application demonstrates simple email and data length Regular Expression validations.

If you've worked with regular expressions before, then you would have probably collected some favorite RegEx patterns. ValidationProvider allows you to load your collection RegEx patterns so that you can re-use it consistently and share it with your developer friends. You would simply edit and add your RegEx collection to the accompanied file "RegExPatternStore.xml" as seen in the animation above.

Custom Validations

OK, I lied! The above code is not the only code you will need. When business logic gets complicated or if it is required to validate controls that the ValidationProvider does not support, custom validation methods can be wired onto ValidationProvider like this:

//
// Create new ValidationRule and wire-up custom validation method.  
// This can be somewhere in the ctor.
//
Noogen.Validation.ValidationRule vr = new Noogen.Validation.ValidationRule();
vr.CustomValidationMethod += 
 new Noogen.Validation.CustomValidationEventHandler(vr_CustomValidationMethod);
this.validationProvider1.SetValidationRule(this.textBox6, vr);

//
// The custom validation method.
//
private void vr_CustomValidationMethod(object sender, 
                 Noogen.Validation.CustomValidationEventArgs e)
{
   e.IsValid = 
        e.Value.ToString().Equals("abc") || e.Value.ToString().Equals("123") ;
   e.ErrorMessage = "%ControlName% is not in ('abc', '123').";
}

Point of interest

For the purpose of demonstration, I have put both the Noogen.Validation.Design and ValidationProvider in a single project. You would probably want to name your build of ValidationProvider to separate the Designer from the Provider. This will reduce the assembly size, since the Designer is not required for deployment.

History

• April 11^th, 2005 - ValidationProvider 1.0 posted.

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