ASP.NET Validator Controls – Part1

Posted: December 5, 2010 in ASP.NET
Tags:

Very old/basic ASP.NET topic, I gave guidance on this to a beginner recently by compilation following content from net and I am sharing here the same for the benefit of other beginners …

ASP.NET Validation Controls are powerful web server controls that are used for validating user input.  These controls provides both server side and client side validation.

The client side validation features can be used to give users an improved UI experience.  By using the client side features, users will not need to wait for a full page postback to occur only to discover that they have failed to fill out form completely.  Instead, the client side features can be using to notify the user immediately (before the page is submitted) about any missing and/or invalid data.

One of the shortcomings of the validation controls under the 1.1 Framework was the inability to validate only portions of your form.  Whenever the validators were triggered, all validators on the page were checked even if they might not be related to the particular button being clicked.  With the 2.0 and above Framework versions, a new ValidationGroup property was introduced.  By setting the ValidationGroup property on a button, only those validation controls that were also set to that same ValidationGroup will be checked.

The validation can be checked on the server side with the help of the IsValid property of the validation control.  Additionally, you can use the IsValid property of the Page to check the validation result of all validation controls on the page.  Before testing the IsValid property of the validation control or the page, it is important that the validation check has already been performed through the use of the Validate method.  You can call Validate on individual controls and also on the page itself.

Validator Control Samples –

RegularExpression Validator – Client Side Validation

<form id=”form1″ runat=”server”>
<div>
Zipcode:<br />
<asp:TextBox runat=”server” id=”txt5″ />
<asp:RegularExpressionValidator runat=”server” id=”RegularExpressionValidator1″ ControlToValidate=”txt5″
errormessage=”Please enter valid zip!” ValidationGroup=”456″ ValidationExpression=”\d{5}”/>
<br /><br />
<asp:Button runat=”server” id=”txtSubmit5″ text=”Ok” ValidationGroup=”456″/>
</div></form>

Compare Validator – Client Side Validation

<form id=”form1″ runat=”server”>
<div>
Age:<br />
<asp:TextBox runat=”server” id=”txtComp” />
<asp:CompareValidator runat=”server” id=”comp1″ ControlToValidate=”txtComp”
errormessage=”Please enter 10!” Operator=”Equal” Type=”String” ValidationGroup=”345″ ValueToCompare=”10″/>
<br /><br />
<asp:Button runat=”server” id=”btnSubmit4″ text=”Ok” ValidationGroup=”345″/>
</div></form>

We can also use ControlToCompare, to directly compare ControlToValidate against other control’s value. For ex many sites will ask for 2 times entry when we create/reset password for user account and submit on page works only when both entries are same.

Required/Range Validator – Server Side Validation

Client Side Validation avoids page back to the server. For performing Validation on serverside we can add enableclientscript=”false” to the RequiredFieldValidator, RangeValidator as explained in below code

<form id=”form1″ runat=”server”>
<div>
Age:<br />
<asp:TextBox runat=”server” id=”txt3″ />
<asp:RequiredFieldValidator runat=”server” id=”reqtxt3″ controltovalidate=”txt3″
errormessage=”Please enter age!” EnableClientScript=”false” ValidationGroup=”234″/>
<asp:RangeValidator runat=”server” id=”rangetxt3″ controltovalidate=”txt3″
errormessage=”Please enter valid age!” EnableClientScript=”false”
MaximumValue=”120″ MinimumValue=”1″  Type=”Integer” ValidationGroup=”234″/>
<br /><br />
<asp:Button runat=”server” id=”btnSubmit3″ text=”Ok” onclick=”btnSubmit3_Click” ValidationGroup=”234″/>
</div></form>

Web Page Code Behind C# code

protected void btnSubmit3_Click(object sender, EventArgs e)
{
if (Page.IsValid)
{
btnSubmit3.Text = “Valid!”;
}
}

 

CustomValidator control is another validator control which is used to validate controls based on some custom logic that does not fall into the generic validations possible using the out of box other validator controls.

Following example explains how we can validate control using CustomValidator control both on client, server side.

Client Side

<form id=”form1″ runat=”server”>

<div>

<div>

Prime Number:<br />

<asp:TextBox runat=”server” id=”txt2″ />

<asp:CustomValidator runat=”server” id=”custtxt2″ controltovalidate=”txt2″

errormessage=”Please enter prime number!” ValidationGroup=”123″ ClientValidationFunction=”CheckPrime”/>

</div>

</div>

</form>

Javascript

<script language=”JavaScript”>

function CheckPrime(sender, args)

{

var iPrime = parseInt(args.Value);

var iSqrt = parseInt(Math.sqrt(iPrime));

for (var iLoop=2; iLoop<=iSqrt; iLoop++)

if (iPrime % iLoop == 0)

{

args.IsValid = false;

return;

}

args.IsValid = true;

}

</script>

ServerSide

<form id=”form2″ runat=”server”>

<div>

<div>

Prime Number:<br />

<asp:TextBox runat=”server” id=”txt1″ />

<asp:CustomValidator runat=”server” id=”custtxt1″ controltovalidate=”txt1″

errormessage=”Please enter prime number!” ValidationGroup=”234″ OnServerValidate=”PrimeNumberCheck”/>

<br /><br />

<asp:Button runat=”server” id=”btnSubmt2″ text=”Ok” onclick=”btnSubmt2_Click” ValidationGroup=”234″ />

</div>

</div>

</form>

Webpage Code Behind C# Code

public void PrimeNumberCheck(object sender, ServerValidateEventArgs args)

{

int iPrime = Convert.ToInt32(args.Value);

int iLoop = 0;

int iSqrt = Convert.ToInt32(Math.Sqrt(iPrime));

for (iLoop = 2; iLoop <= iSqrt; iLoop++)

{

if (iPrime % iLoop == 0)

{

args.IsValid = false;

return;

}

}

args.IsValid = true;

}

protected void btnSubmt2_Click(object sender, EventArgs e)

{

if (Page.IsValid)

{

btnSubmt2.Text = “Valid!”;

}

}

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