Validates form fields (TextBox or DataGridView controls) by attributes you define on them, manifesting with both an individual error indication and a disabling of a designated common form submittal (ok) button.

public class Validator

public class Validator

Public Class Validator

Public Class Validator

public ref class Validator

public ref class Validator

Tired of writing custom validation code for every input field in your applications? This class provides a generic validation engine that can automate many validation scenarios. Besides the description here, I have also published an article discussing the practical uses of this tool -- Exploring Secrets of Windows Form Validation -- available on the DevX online magazine.

A validation error may be displayed in either an individual Label component unique to each control, or by using the standard ErrorProvider component. The latter has the advantage that you do not have to create and associate a Label component with each validating component, but the disadvantage that you must use the mouse to see the validation error.

In order to validate a control, you add it to a Validator instance, then call one of the Validate methods inside either the TextChanged or Validating event handler. MSDN documentation suggests the Validating event handler is the appropriate place. Note that the handler will be called only when focus leaves a control. So if you want finer control (as in every keystroke) then TextChanged is a better choice.

In addition to adding the control to the Validator, you must attach attributes to the control that specify just what you want to validate. This is done using the Tag property. You specify a list of 1 or more attributes from those below that you want to validate. All of the ones you specify will be evaluated, but only one error will be reported at a time.

Each singular Control (e.g. TextBox) must have a validation attribute list (stored on the Tag property) in the following format:

<attr1>=<value1>;<attr2>=<value2>;...;<attrN>=<valueN>

<attr1>=<value1>;<attr2>=<value2>;...;<attrN>=<valueN>

maxLen

field must contain no more than the specified number of characters

minLen

field must contain at least the specified number of characters

maxVal

field must contain a number that is no larger than the specified value

minVal

field must contain a number that is no smaller than the specified value

pattern

field must match the specified regular expression

A collective control, such as a DataGridView, uses the same list of attributes, but the Tag definition is more complex. Each column in the DataGridView requires its own attribute list. The format is:

[<column1>]<attrList1>;[<column2>]<attrList2>;...[<columnN>]<attrListN>;

[<column1>]<attrList1>;[<column2>]<attrList2>;...[<columnN>]<attrListN>;

The table below illustrates some sample validation attribute lists. Except for pattern, the attribute meanings should be clear. The pattern attribute is a regular expression (see .NET Framework Regular Expressions) providing a powerful, flexible mechanism for matching almost any input.

Usage:

In the Load event handler for your Form include:

validator = new Validator(okButton);
validator.Add(xyzTextBox, xyzErrLabel);
validator.Add(otherTextBox, otherErrLabel);
. . . // Add additional controls to be validated.
validator.ValidateAll();

validator = new Validator(okButton);
validator.Add(xyzTextBox, xyzErrLabel);
validator.Add(otherTextBox, otherErrLabel);
. . . // Add additional controls to be validated.
validator.ValidateAll();

validator.Validate((TextBox)sender);

validator.Validate((TextBox)sender);

Since CleanCode 0.9.07.

[Cmd]pattern=^\w;[Item]pattern=^\w+$;[MatchExpr]pattern=\(.*\);[Format]pattern=\{\d.*\}

[Cmd]pattern=^\w;[Item]pattern=^\w+$;[MatchExpr]pattern=\(.*\);[Format]pattern=\{\d.*\}