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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

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Asp net validation controls introduction
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 introduction1
ASP.NET Validation Controls (Introduction)

  • If client-side validation is enabled, we don’t postback until the client ‘thinks’ the values are valid

  • Always validate on the server-side too to thwart those hackers doing a post on their own


Asp net validation controls server processing model 1
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
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


Checking the validators example
Checking the Validators (Example)

  • Display the validation messages:

    For Each v In Page.Validators

    Response.Write(v.ErrorMessage)

    Next

    foreach (Ivalidator v in Page.Validators)

    {

    Response.Write(v.ErrorMessage)

    }


Asp net validation controls concepts
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
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 comparevalidator
ASP.NET Validation Controls (CompareValidator)

  • The CompareValidator validates that the values of two other control instances are the same

    • Set the ControlToValidate and ControlToCompare properties

    • Optionally use a RequiredFieldValidator so that empty controls will not be valid


Asp net validation controls customvalidator
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 customvalidator1
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 customvalidator example client
ASP.NET Validation Controls(CustomValidator) (Example Client)

function validateLength(src,args)

{

if (args.Value.length <=6)

{

args.IsValid = true;

document.title = "true=" + args.Value.length;

}

else

{

args.IsValid = false;

document.title = "false" + args.Value.length;

}

}


Asp net validation controls regularexpressionvalidator
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 client1
ASP.NET Validation Controls(CustomValidator) (Example Client)

Protected Sub CustomValidator1_ServerValidate(ByVal source As Object, ByValargs As System.Web.UI.WebControls.ServerValidateEventArgs) Handles CustomValidator1.ServerValidate

If args.Value.Length > 6 Then

args.IsValid = True

Else

args.IsValid = False

End If

End Sub


Regular expressions introduction
Regular Expressions (Introduction)

  • Regular expressions are used throughout computer science and programming languages as a means of pattern matching

  • Patterns are matched using a regular expression engine

    • You generally don't run the engine directly

    • Different implementations have different "flavors”


Regular expressions implementations
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
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"


Regular expressions quantifiers
Regular Expressions (Quantifiers)

  • Quantifiers denote how many times a character or pattern can repeat

  • Quantifiers (list)

    • * (0 or more)

    • + (1 or more)

    • ? (0 or 1)


Quantifiers example
Quantifiers (Example)

  • 1?5?

    • 1 can appear 0-1 times and 5 can appear 0-1 times

    • This pattern also matches an empty string because 1 or 5 can appear 0 times


Quantifiers numeric range
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


Special characters introduction
Special Characters (Introduction)

  • Some characters (*, ?, +, and others) have special meaning when creating regular expressions

    • These characters are called metacharacters

  • To include these characters as literal characters in a regular expression, they must be escaped

    • The \ is the escape character


Special characters list
Special Characters (List)

  • \n

  • \r

  • \t

  • \\

  • \|

  • \-

  • \^

  • \?

  • \*

  • \+

  • \{

  • \}

  • \(

  • \)

  • \[

  • \]

  • linefeed

  • carriage return

  • tab

  • The backward slash \

  • The vertical bar |

  • The hyphen -

  • The caret ^

  • The question mark ?

  • The asterisk *

  • The plus sign +

  • The open curly brace {

  • The close curly brace }

  • The open paren (

  • The close paren )

  • The open square bracket [

  • The close square bracket ]


Special characters
Special Characters (.)

  • The dot (.) matches any character (except for the newline character)

  • Thus, the following would match any character followed by the digit 0.0


Character classes list 1
Character Classes (List 1)

  • \smatches a space

  • \S matches any character that is not a space

  • \d matches any digit

  • \D matches any character that is not a digit

  • \w matches a word

  • \W matches any character sequence that is not a word


User defined character classes 1
User Defined Character Classes (1)

  • We can tell the regular expression engine to match a range of characters

  • Square brackets surround the range

  • Only one character can appear in the range


User defined character classes 2
User Defined Character Classes (2)

  • A hyphen can appear in a character class to denote a range

    • Multiple ranges can appear in a character class

    • The order of ranges is not significant

  • Examples

    • A name beginning with a letter followed by any sequence of upper-case or lower-chase characters


Negation
Negation

  • The caret "^" is the negation character when used in a character class

  • A "q" followed by any sequence of characters that is not a "u"


Start of pattern and end of pattern
Start of Pattern and End of Pattern

  • Anchors are used to match a position

  • "^" matches the start of a pattern

  • "$" matches the end of the pattern


Alternation
Alternation

  • Alternation is basically a logical or

  • The vertical bar is the alternation symbol

  • Example:

  • The following matches "cat" or "dog"

  • <xs:pattern value="cat|dog" />


Net and regular expressions
.NET and Regular Expressions

  • The System.Text.RegularExpressions namespace contains classes designed to match regular expressions against a string

  • A Match object is returned by a pattern-matching operation


Testing a regular expression
Testing a Regular Expression

  • The following statement runs a regular expression against a string and returns a Match:

    Dim Result As _

    System.Text.RegularExpressions. _ Match

    Result = _System.Text.RegularExpressions. _Regex.Match(txtString.Text, _txtPattern.Text)


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