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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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