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Asp.NET Core Vaidation

Controls

ASP.NET Validation

Controls (Introduction)

 The ASP.NET validation controls can be used to validate data on the client, the server, or both  Client-side validation is performed using automatically generated JavaScript  Server-side validation is performed using VB or C# code in the proper event handler  Server-side validation is always enabled while client-side validation is optionally enabled

ASP.NET Validation Controls

(Server Processing Model 1)

 Validation controls apply their rules and validate a corresponding control  Call the Page.Validate() method to force the validation controls to execute  This is usually not necessary  Test Page.IsValid to determine whether the page has valid data or not

ASP.NET Validation Controls

(Server Processing Model 2)

 Page states  Controls are initialized and populated when the page is loaded  After the page loads, the controls are validated and the Page.IsValid property is set  The Page.Validators property contains results of each control’s validator  Each item in the collection implements IValidator

ASP.NET Validation Controls

(Concepts)

 Set the ControlToValidate property the control instance that will be validated  Set EnableClientScript to enable client- side validation  ASP will generate the necessary JavaScript  Set the ErrorMessage property to the error message that will appear in the validation control

ASP.NET Validation Controls

( RequiredFieldValidator and

RangeValidator )

 RequiredFieldValidator checks that a control has a value  RangeValidator checks that a controls value is within a valid range  Set the MinimumValue and MaximumValue properties to the valid range  A control with no valid is considered valid  Use with the RequiredFieldValidator to prevent this  Set the Type property to define the data type to be stored in the control to validate

ASP.NET Validation Controls

( CustomValidator )

 The CustomValidator control allows you to easily create custom and client script and server event handlers  Set the ControlToValidate as usual  Set the ClientValidationFunction to the name of the JavaScript function appearing on the client  Server-side validation is automatic  You must write the code for the ServerValidate event handler

ASP.NET Validation Controls

( CustomValidator )

 The client validation function must accept two arguments  The first contains the object that fired the event  The second contains the event data

ASP.NET Validation Controls

( RegularExpressionValidator )

 It validates another control instance against a regular expression  The regular expression is stored in the ValidationExpression property

ASP.NET Validation Controls ( CustomValidator ) (Example Client)

Protected Sub CustomValidator1_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventAr gs) Handles CustomValidator1.ServerValidate

If args.Value.Length > 6 Then args.IsValid = True Else args.IsValid = False End If End Sub

Regular Expressions

(Implementations)

 Some consider Perl 5 as the basis or standard for regular expressions  .NET supports regular expressions  JavaScript supports regular expression  UNIX scripting languages support regular expressions  And of course XML supports them

Regular Expressions

(Literal Values)

 The most simple of regular expressions will match a literal value  By default, regular expressions are case sensitive  The regular expression "cat" contains three literal characters  It will match the following patterns  "concatenate"  "the cat ran away"

Quantifiers (Example)

 1 can appear 0-1 times and 5 can appear 0- times  This pattern also matches an empty string because 1 or 5 can appear 0 times

Quantifiers (Numeric Range)

 Quantifiers allow us to specify how many times a pattern can occur  Numeric range quantifiers appear in curly braces

 {n} Must occur exactly n times

 {n,m} Must occur between n and m times

 {n,} Must occur n or greater times