Validation Controls

• Validating a form is most important part of

website development. User enters data of his or
her choice, you need that entered data in
specific format.
• To check whether of given data is in specific
format or not you ca use validation controls.
• Initially for validating control we used to write
javascript .
• But it took more number of lines of code and
more time.
• With validation control this could be done in just
2 minutes.
• Validation controls are most important and
useful feature developed by asp.net.
• It reduces the 90% of the client side
validation.
• Form validation can be done in 2 ways:
– Client side
– Server side
• ASP.NET validation controls validate the user input data to ensure
that useless, unauthenticated, or contradictory data don’t get stored.
• ASP.NET provides the following validation controls:

•  RequiredFieldValidator

•  RangeValidator

•  CompareValidator

•  RegularExpressionValidator

•  CustomValidator

•  ValidationSummary
 BaseValidator Class
• The validation control classes are inherited
from the BaseValidator class hence they
inherit its properties and methods. Therefore,
it would help to take a look at the properties
and the methods of this base class, which are
common for all the validation controls:
• Members Description
• ControlToValidate Indicates the input control to validate.
• Display Indicates how the error message is shown.
• EnableClientScript Indicates whether client side validation
will take.
• Enabled Enables or disables the validator.
• ErrorMessage Indicates error string.
• Text Error text to be shown if validation fails.
• IsValid Indicates whether the value of the control is valid.

• SetFocusOnError It indicates whether in case of an

invalid control, the focus should switch to the related input
control.
• ValidationGroup The logical group of
multiple validators, where this control
belongs.
• Validate() This method revalidates the control
and updates the IsValid property.
 RequiredFieldValidator Control
• The RequiredFieldValidator control ensures that
the required field is not empty. It is generally tied
to a text box to force input into the text box.
• The syntax of the control is as given:
• <asp:RequiredFieldValidator ID="rfvcandidate"
• runat="server" ControlToValidate ="ddlcandidate"
• ErrorMessage="Please choose a candidate"
• InitialValue="Please choose a candidate">
• </asp:RequiredFieldValidator>
 RangeValidator Control
• The RangeValidator control verifies that the input value
falls within a predetermined range.
• It has three specific properties:
• Properties Description
• Type It defines the type of the data. The available
values are: Currency, Date, Double, Integer, and String.
• MinimumValue It specifies the minimum value of the
range.
• MaximumValue It specifies the maximum value of the
range.
• <asp:RangeValidator ID="rvclass"
• runat="server"
• ControlToValidate="txtclass"
• ErrorMessage="Enter your class (6 - 12)"
• MaximumValue="12"
• MinimumValue="6" Type="Integer">
• </asp:RangeValidator>
 CompareValidator Control
• The CompareValidator control compares a value in one control
with a fixed value or a value in another control.
• It has the following specific properties:
• Properties Description
• Type It specifies the data type.
• ControlToCompare It specifies the value of the input control
to compare with.
• ValueToCompare It specifies the constant value to compare
with.
• Operator It specifies the comparison operator, the available
values are: Equal, NotEqual, GreaterThan, GreaterThanEqual,
LessThan, LessThanEqual, and DataTypeCheck.
• The basic syntax of the control is as follows:
• <asp:CompareValidator
ID="CompareValidator1"
• runat="server"
• ErrorMessage="CompareValidator">
• </asp:CompareValidator>
 RegularExpressionValidator
• The RegularExpressionValidator control allows
validating the input text by matching against a
pattern of a regular expression. The regular
expression is set in the ValidationExpression
property.
• The following table summarizes the commonly
used syntax constructs for regular expressions:
Character Escapes Description
• \b Matches a backspace
• \t Matches a tab
• \r Matches a carriage return
• \v Matches a vertical tab
• \f Matches a form feed
• \n Matches a new line
• \ Escape character
• Apart from single character match, a class of characters could be
specified that can be matched, called the metacharacters.
• Metacharacters Description
• . Matches any character except \n.
• [abcd] Matches any character in the set.
• [^abcd] Excludes any character in the set.
• [2-7a-mA-M] Matches any character specified in the range.
• \w Matches any alphanumeric character and underscore.
• \W Matches any non-word character.
• \s Matches whitespace characters like, space, tab, new line etc.

• \S Matches any non-whitespace character.

• \d Matches any decimal character.

• \D Matches any non-decimal character.
• Quantifiers could be added to specify number of
times a character could appear.
• Quantifier Description
• * Zero or more matches
• + One or more matches
• ? Zero or one matches
• {N} N matches
• {N,} N or more matches
• {N,M} Between N and M matches
• The syntax of the control is as given:
• <asp:RegularExpressionValidator ID="string"
• runat="server"
• ErrorMessage="string"
• ValidationExpression="string"
• ValidationGroup="string">
• </asp:RegularExpressionValidator>
 CustomValidator
• The CustomValidator control allows writing
application specific custom validation routines
for both the client side and the server side
validation.
• The client side validation is accomplished
through the ClientValidationFunction property.
The client side validation routine should be
written in a scripting language, such as JavaScript
or VBScript, which the browser can understand.
• The server side validation routine must be called
from the control’s ServerValidate event handler.
The server side validation routine should be
written in any .Net language, like C# or VB.Net.
• The basic syntax for the control is as given:
• <asp:CustomValidator ID="CustomValidator1"
• runat="server"
• ClientValidationFunction=.cvf_func.
• ErrorMessage="CustomValidator">
• </asp:CustomValidator>
 ValidationSummary
• The ValidationSummary control does not perform any validation but shows
a summary of all errors in the page. The summary displays the values of
the ErrorMessage property of all validation controls that failed validation.
• The following two mutually inclusive properties list out the error message:

•  ShowSummary: shows the error messages in specified format.

•  ShowMessageBox: shows the error messages in a separate window.

• The syntax for the control is as given:

• <asp:ValidationSummary ID="ValidationSummary1"
• runat="server"
• DisplayMode = "BulletList"
• ShowSummary = "true"
• HeaderText="Errors:" />
 Validation Groups
• Complex pages have different groups of
information provided in different panels. In such
situation, a need might arise for performing
validation separately for separate group. This kind
of situation is handled using validation groups.
• To create a validation group, you should put the
input controls and the validation controls into the
same logical group by setting their
ValidationGroup property.