Question

I have one text box on that text box i am using required field validation.
If text box is empty then i want to show in the text box “Please enter some text”, and if something is in text box then i want to check that text box text is valid email id or not if not then i want to show inside text box “Please enter valid email id”

Answer 1

You can carry out the following using jQuery:

<script type="text/javascript">

function CheckEmail()
{
    var $email = $("#<%=EmailText.ClientID %>");

    if ($email.val().length) {
        if (!IsEmailValid($email.val()))
            $email.val("Please enter a valid email address");
    }
    else {
        $email.val("Please enter some text.");
    }
}    

function IsEmailValid(inputvalue) 
{
    var pattern=/^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+/;

    if(pattern.test(inputvalue)) {
        return true;
    } 
    else {
        return false;
    }
}

</script>

<asp:TextBox ID="EmailText" Text="Please enter some text" runat="server" />
<asp:Button ID="SubmitButton" runat="server" OnClientClick="CheckEmail()" />

Or you could use out of the box .NET validation using the RequiredFieldValidator and RegularExpressionValidator.

Edit

Since the poster has stated client-side scripting cannot be used for validation, I’ve added server-side validation:

protected void SubmitButton_Click(object sender, EventArgs e)
{
        if (IsFormValid())
        {
        //Do something...
    }

}

private bool IsFormValid()
{
    bool isValid = true;

    if (String.IsNullOrEmpty(EmailText.Text))
    {
        EmailText.Text = "Please enter an email address";
        isValid = false;
    }
    else
    {
        if (!Regex.IsMatch(EmailAddress.Text, @"/^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+/"))
        {   
            EmailText.Text = "Email address not valid";
            isValid = false;    
        }
    
    }

    return isValid;
}