Validation Control in ASP.NET

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 M.SARULATHA
Assistant Professor
Dept. of CA, JJC.

RequiredFieldValidation Control

 

            The RequiredFieldValidator control is simple validation control, which checks to see if the data is entered for the input control. You can have a RequiredFieldValidator control for each form element on which you wish to enforce Mandatory Field rule.

<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" 

Style="top: 98px; left: 367px; position: absolute; height: 26px; width: 162px" 

ErrorMessage="password required" ControlToValidate="TextBox2">

</asp:RequiredFieldValidator>  

CompareValidator Control

 

            The CompareValidator control allows you to make comparison to compare data entered in an input control with a constant value or a value in a different control.

 

            It can most commonly be used when you need to confirm password entered by the user at the registration time. The data is always case sensitive.

 

<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" Style="top: 145px;  

        left: 367px; position: absolute; height: 26px; width: 162px" ErrorMessage="password required"  

        ControlToValidate="TextBox3"></asp:RequiredFieldValidator>  

RangeValidator Control

 

            The RangeValidator Server Control is another validator control, which checks to see if a control value is within a valid range. The attributes that are necessary to this control are: MaximumValue, MinimumValue, and Type.

<asp:RangeValidator ID="RangeValidator1" runat="server" 

Style="top: 194px; left: 365px; position: absolute; height: 22px; width: 105px" 

ErrorMessage="RangeValidator" ControlToValidate="TextBox4" MaximumValue="100" MinimumValue="18" Type="Integer"></asp:RangeValidator>  

 

 

RegularExpressionValidator Control

 

            A regular expression is a powerful pattern matching language that can be used to identify simple and complex characters sequence that would otherwise require writing code to perform.

 

            Using RegularExpressionValidator server control, you can check a user's input based on a pattern that you define using a regular expression.

 

            It is used to validate complex expressions. These expressions can be phone number, email address, zip code and many more. Using Regular Expression Validator is very simple. Simply set the ValidationExpression property to any type of expression you want and it will validate it.

 

            If you don't find your desired regular expression, you can create your custom one.

 

In the example I have checked the email id format:

<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" Style="top: 234px;  

        left: 366px; position: absolute; height: 22px; width: 177px"   

        ErrorMessage="RegularExpressionValidator" ControlToValidate="TextBox5"   

        ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>  

The complete code for the above 4 controls is as,

 

Default.aspx Design

validationcontrols_gui.gif

Default.aspx Source code

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>  

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  

<html xmlns="http://www.w3.org/1999/xhtml">  

<head runat="server">  

    <title>Untitled Page</title>  

</head>  

<body>  

    <form id="form1" runat="server">  

    <div>  

        <asp:Label ID="Label3" runat="server" Style="top: 241px; left: 70px; position: absolute;  

            height: 22px; width: 128px; bottom: 282px;" Text="Enter your email id:"></asp:Label>  

        <asp:Label ID="Label1" runat="server" Style="top: 54px; left: 74px; position: absolute;  

            height: 22px; width: 128px" Text="Enter your name:"></asp:Label>  

        <asp:TextBox ID="TextBox1" runat="server" Style="top: 54px; left: 221px; position: absolute;  

            height: 22px; width: 128px; right: 396px;"></asp:TextBox>  

        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" Style="top: 56px;  

            left: 378px; position: absolute; height: 22px; width: 128px" ErrorMessage="RequiredFieldValidator"  

            ControlToValidate="TextBox1">name is   

        mandatory </asp:RequiredFieldValidator>  

    </div>  

    <p>  

        <asp:Button ID="Button1" runat="server" Style="top: 311px; left: 267px; position: absolute;  

            height: 26px; width: 61px" Text="Submit" />  

    </p>  

    <asp:TextBox ID="TextBox3" runat="server" Style="top: 145px; left: 217px; position: absolute;  

        height: 22px; width: 131px" TextMode="Password"></asp:TextBox>  

    <p>  

        <asp:TextBox ID="TextBox2" runat="server" Style="top: 101px; left: 218px; position: absolute;  

            height: 22px; width: 131px" TextMode="Password"></asp:TextBox>  

        <asp:Label ID="Label4" runat="server" Style="top: 105px; left: 74px; position: absolute;  

            height: 22px; width: 128px" Text="Password"></asp:Label>  

        <asp:TextBox ID="TextBox5" runat="server" Style="top: 239px; left: 210px; position: absolute;  

            height: 22px; width: 134px"></asp:TextBox>  

    </p>  

    <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" Style="top: 98px;  

        left: 367px; position: absolute; height: 26px; width: 162px" ErrorMessage="password required"  

        ControlToValidate="TextBox2"></asp:RequiredFieldValidator>  

    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" Style="top: 145px;  

        left: 367px; position: absolute; height: 26px; width: 162px" ErrorMessage="password required"  

        ControlToValidate="TextBox3"></asp:RequiredFieldValidator>  

    <asp:CompareValidator ID="CompareValidator1" runat="server" Style="top: 149px; left: 512px;  

        position: absolute; height: 26px; width: 162px" ErrorMessage="CompareValidator"  

        ControlToValidate="TextBox3" ValueToCompare="hello"></asp:CompareValidator>  

    <p>  

        <asp:Label ID="Label5" runat="server" Style="top: 148px; left: 71px; position: absolute;  

            height: 22px; width: 128px; bottom: 375px;" Text="Confirm Password"></asp:Label>  

        <asp:TextBox ID="TextBox4" runat="server" Style="top: 194px; left: 212px; position: absolute;  

            height: 22px; width: 140px"></asp:TextBox>  

        <asp:Label ID="Label6" runat="server" Style="top: 194px; left: 71px; position: absolute;  

            height: 22px; width: 128px; bottom: 329px;" Text="Enter your age:"></asp:Label>  

    </p>  

    <asp:RangeValidator ID="RangeValidator1" runat="server" Style="top: 194px; left: 365px;  

        position: absolute; height: 22px; width: 105px" ErrorMessage="RangeValidator"  

        ControlToValidate="TextBox4" MaximumValue="100" MinimumValue="18" Type="Integer"></asp:RangeValidator>  

    <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" Style="top: 234px;  

        left: 366px; position: absolute; height: 22px; width: 177px"   

        ErrorMessage="RegularExpressionValidator" ControlToValidate="TextBox5"   

        ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>  

    </form>  

</body>  

</html>  

CustomValidator Control

 

            You can solve your purpose with ASP.NET validation control. But if you still don't find solution you can create your own custom validator control.

 

            The CustomValidator Control can be used on client side and server side. JavaScript is used to do client validation and you can use any .NET language to do server side validation.

 

            I will explain you CustomValidator using server side. You should rely more on server side validation.

 

To write CustomValidator on server side you override ServerValidate event.

 

customervalidator_gui.gif

 

Code behind file

using System;  

using System.Configuration;  

using System.Data;  

using System.Linq;  

using System.Web;  

using System.Web.Security;  

using System.Web.UI;  

using System.Web.UI.HtmlControls;  

using System.Web.UI.WebControls;  

using System.Web.UI.WebControls.WebParts;  

using System.Xml.Linq;  

  

public partial class _Default : System.Web.UI.Page  

{  

    protected void UserCustomValidate(object source, ServerValidateEventArgs args)  

    {  

        string str = args.Value;  

        args.IsValid = false;  

       //checking for input length greater than 6 and less than 25 characters  

        if (str.Length < 6 || str.Length > 25)  

        {  

            return;  

        }  

        //checking for a atleast a single capital letter  

        bool capital = false;  

        foreach (char ch in str)  

        {  

            if (ch >= 'A' && ch <= 'Z')  

            {  

                capital = true;  

                break;  

            }  

        }  

        if (!capital)  

        {  

            return;  

        }  

       //checking for a atleast a single lower letter  

        bool lower = false;  

         foreach (char ch in str)  

        {  

            if (ch >= 'a' && ch <= 'z')  

            {  

                lower = true;  

                break;  

            }  

        }  

        if (!lower)  

        {  

            return;  

        }  

        bool digit = false;  

        foreach (char ch in str)  

        {  

            if (ch >= '0' && ch <= '9')  

            {  

                digit = true;  

                break;  

            }  

        }  

         if (!digit)  

        {  

            return;  

        }  

        args.IsValid = true;  

    }  

    protected void Page_Load(object sender, EventArgs e)  

    {  

    }  

   protected void Button1_Click(object sender, EventArgs e)  

    {  

    }  

}

customervalidator_output.gif

            The server side validation you write does not need to provide the exact same validation as that of the client side validation. The client side validation can check for the user input data for range and type and server side validation can check for matching of data with database. Both server side and client side validation can be used for total solution.

 

 

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