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Validation Controls in ASP.NET

Updated on February 27, 2015

How to set RequiredFieldValidator in ASP.NET?

The RequiredFieldValidator control is used when a field must not be left blank.

Lets assume that we have a DropDownList named 'Gender' in our Registration Form and it is a required field so that user must select it. First we have to set the following DropDownList properties:

ID
Gender
Items
(Collection)...
  • Click on the collection button then ListItem Collection Editor would be opened as shown below:

  • Click on the Add button and set the ListItem properties as follows:

  • Click 'OK' and set the RequiredFieldValidator properties as follows:

ID
Gender_Validator
ControlToValidate
Gender
ErrorMessage
Please Select Gender
InitialValue
0

Now if user does not select either 'Male' or 'Female' then RequiredFieldValidator would generate an error message.

Code Snippet:

<asp:RequiredFieldValidator ID="Gender_Validator" runat="server" 
ControlToValidate="Gender" ErrorMessage="Please Select Gender" 
InitialValue="0"></asp:RequiredFieldValidator>

How to use CompareValidator in ASP.NET?

When the values of two controls have to be compared or the value of a control has to be compared to a specified constant value, the CompareValidator control is used.

Example 1:

Suppose that you want your user to be at least 18 years old to join your website, then you have to check the age entered by the user to see whether he/she is 18 years old or not. This could be done very easily by using CompareValidator control. You just need to set the following CompareValidator properties:

ID
Age_Validator
ControlToValidate
Age
ErrorMessage
Age should be 18 or more
Operator
GreaterThanEqual
Type
Integer
ValueToCompare
18

Example 2:

If you don't want your user to be more than 60 years old, then CompareValidator properties would be:

ID
Age_Validator
ControlToValidate
Age
ErrorMessage
Age can't be greater than 60
Operator
LessThanEqual
Type
Integer
ValueToCompare
60

Example 3:

CompareValidator is also used to compare two passwords. CompareValidator properties to compare passwords are:

ID
Password_Validator
ControlToCompare
Password
ControlToValidate
Confirm_Password
ErrorMessage
The two passwords do not match
Operator
Equal
Type
String

How to use RangeValidator in ASP.NET?

The RangeValidator control is used to check if the value entered in a control is in the specified range of values.

Example:

Suppose that you want your user must be in between 18 to 60 years, then you can use RangeValidator to validate user's age during the registration by setting the following RangeValidator's properties:

ID
Age_Validator
ControlToValidate
Age
ErrorMessage
Your age must be in the range of 18-60 Years
Maximum
60
Minimum
18

MinimumValue and MaximumValue are used to set the lower and the upper limit of the range respectively.

Code Snippet:

<asp:rangevalidator controltovalidate="Age" runat="server"
errormessage="Your age must be in the range of 18-60 years"
id="Age_Validator" maximumvalue="60" minimumvalue="18">
</asp:rangevalidator>

How to use RegularExpressionValidator in ASP.NET?

The RegularExpressionValidator checks if the value entered matches the regular expression that is specified.

RegularExpressionValidator characters and their meanings:

Sign
Meaning
^
Specifies that checking starts from here.
$
Specifies that checking ends here.
[ ]
Checks that the value entered match with any of the characters that are in the square brackets.
\w
Allows any value to be entered.
\d{ }
"\d" specifies that the value entered is a digit and { } specifies the number of occurences of the specified data type.
+
Specifies that one or more elements to be added to the expression being checked.

Example:

Suppose that we need To validate Email ID in our registration form, to do so set the following RegularExpressionValidator properties:

ID
Email_Validator
ControlToValidate
Email_ID
ErrorMessage
Please enter the valid email address
ValidationExpression
^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$

Code Snippet:

<asp:RegularExpressionValidator ID="Email_Validator"
runat="server" ControlToValidate="Email_ID"
ErrorMessage="Please enter the valid email address"
ValidationExpression="^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$">
</asp:RegularExpressionValidator>	

(Note: Email_ID is a TextBox ID in which email id would be entered by the user).

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