.NET/ASP.NET Interview Question - Types of Validators in ASP.NET with examples.

Answer:

A validator is a computer program used to check the,validity or syntactical correctness of a fragment of code or text.

IN ASP.NET there are six different types of Validators.

1. Required Field Validator.

2. Regular Expression Validator.

3. Compare Validator.

4. Range Validator.

5. CustomValidator.

6. Validation Summary

RequiredFieldValidator:-Ensure that the control,has a value to assign in it or user does not skip an entry.

For Example:-

 <asp:Textbox id="txtMobileNumber" runat="server"></asp:Textbox>
<asp:RequiredFieldValidator id="RequiredFieldValidator1" runat="server"
ControlToValidate="txtMobileNumber"
ErrorMessage="Mobile Number is a required field."
ForeColor="Red">
</asp:RequiredFieldValidator>

Regular ExpressionValidator:-Ensure that the ,value of the control matches the expression of validator that is specified. This ,type of validation enables you to check for sequence of character, such as ,e-mail address, telephone number, postal code and so on.

For Example:-

 <asp:TextBox ID="txtE-Mail" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
ControlToValidate="txtPassword"
ErrorMessage="Please Enter a Valid E-Mail"
ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"> // for internet E-Mail.
</asp:RegularExpressionValidator>

CompareValidator:-Ensure that the value of one control should be equal to value of another control.which is commonly used in password,less than,greater ,than or equal to.

For Example:-

<asp:TextBox ID="txtPassword" runat="server"></asp:TextBox>
<asp:TextBox ID="txtConfirmPassword" runat="server"></asp:TextBox>
<asp:CompareValidator ID="CompareValidator1" runat="server"
ControlToCompare="txtPassword" ControlToValidate="txtConfirmPassword"
ErrorMessage="Password does not match">
</asp:CompareValidator>

RangeValidator:-Ensures that the value of the control is in specified lower and upper boundaries or specified range. You can check ranges within pairs of numbers, alphabetic characters.

For Example:-

<asp:TextBox ID="txtAmount" runat="server"></asp:TextBox>
<asp:RangeValidator ID="RangeValidator1" runat="server"
ControlToValidate="txtPassword"
ErrorMessage="RangeValidator" MaximumValue="5000"
MinimumValue="100">
</asp:RangeValidator>>

CustomValidator:-This control is used to perform user defined validations.

ValidationSummary:-This validator is used to displays a detailed summary on the validation errors that currently exist.

Regards,

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