Validation
in Asp.NET
In
this article I will explain different type of validations in asp.net. We will
learn why we need validations in website development. The main motive of using
validations is to validate input data from users. We validate controls so that
they accept only correct data or data in valid format.
Why we need Validations:
Validation is required when we want input in particular format.
Suppose we want to enter numeric no in TextBox control. So in that case we
require validation. Suppose we want to enter email address in textbox then in
that we will have to validate that particular textbox. We can validate controls
for data type, empty control, special format, range etc.
Types of validations in Asp.NET:
1. Client side
validator
2. Server Side
validator
Server side validations: Server side
validations are more secure. We use code in code behind to validate the data.
So it is bit slow when compared to client side.
Client
side validations:
Client side validations are fast and easy to implement. Asp.Net Provides some
validation controls to implement client side validations.
Validations
controls in Asp.NET
-
RequiredFieldValidator
-
RangeValidator
-
CompareValidator
-
RegularExpressionValidator
-
CustomValidator
-
ValidationSummary
Main
three properties are common in most of the controls:
ControlToValidate: Id
of the control which we want to validate
Error
Message:
Error message which will be shown when error occurs
Text: Text
which will be shown.
1. Required
Field Validator:
Required
field validator is used to when we want to check whether control is empty or
not. It ensures that the control is empty or not. We generally validate textbox
with this control. We can also validate dropdownlist control.
Syntax
to validate TextBox using Requiredfieldvalidator:
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="Enter Name" ControlToValidate="txtName">*</asp:RequiredFieldValidator>
2. RangeValidator
Control
The
RangeValidator control verifies that the input value falls within a
predetermined range.
Syntax for Range validator:
<asp:RangeValidator ID="rvValue" runat="server" ControlToValidate="txtValue"
ErrorMessage="Enter Value between (10 - 20)" MaximumValue="20"
MinimumValue="10" Type="Integer">
3. CompareValidator
Control
The
CompareValidator control compares a value in one control with a fixed value or
a value in another control.
Syntax CompareValidator Control:
<asp:CompareValidator ID="CompareValidator1" runat="server"
ErrorMessage="CompareValidator" ControlToCompare="txtConfirmPassword"
ControlToValidate="txtName"></asp:CompareValidator>
4. RegularExpressionValidator
The
RegularExpressionValidator is used in case of validating the input text by
matching against a pattern of a regular expression. The regular expression is
set in the ValidationExpression property.
We can
use other regular expression to validate data which are not listed in
ValidationExpression property.
Syntax for regular expressions:
<asp:RegularExpressionValidator
ID="RegularExpressionValidator1" runat="server"
ErrorMessage="Enter Valid Email" ControlToValidate="txtEmail"
ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>
5. CustomValidator:
The
CustomValidator control is used to write custom validation for both the client
side and the server side validation.
For
client side validation we use ClientValidationFunction property. For server
side we use onservervalidate property. We call function created on server side.
Syntax For custom
Validator:
<asp:CustomValidator runat="server" id="customname" controltovalidate="txtName" onservervalidate="function_name" errormessage="The text must be exactly 10 characters long!" />
6. Validation
Summary: Validation summary is not used to validate controls. It is used to
show all error message in one place.
Main prioperties are:
ShowMessageBox: it
will show error in message box.
ShowSummary:It
will show messages as a list.