Conditionally disable validation - asp.net

Question

I have form with few text boxes which goes through validation (both server and client sides). In the form I have buttons: "Next", "Back", "CanceL". So I don't need validation to fireup then user clicks "back" or "cancel" buttons. How can I achieve this?
Thanks in advance!
Some sample:
<div class="buttons">
<input type="submit" name="cancelButton" value="" />
<input type="submit" name="backButton" value="" />
<input type="submit" name="nextButton" value="" />
</div>
<% using (Html.BeginForm()) { %>
<p>
<table style="width: 200px">
<tr><td align="center" colspan=2><%= Html.ValidationMessageFor(m => m.street) %><%= Html.DropDownListFor(m => m.street, Model.streetsList) %></td></tr>
<tr><td colspan=2> </td></tr>
<tr><td valign="bottom" align="right" style="width: 75px"><%= Html.LabelFor(m => m.flatNumber) %>:</td><td align=left><%= Html.TextBoxFor(m => m.flatNumber, new { maxlength = 6, style = "width: 48px;" })%> <%= Html.ValidationMessageFor(m => m.flatNumber) %></td></tr>
</table>
<br />
<input type="submit" class="refusal button red floatL" name="cancelButton" value="" />
<input type="submit" class="back button green floatL" name="backButton" value="" />
<input type="submit" class="continue button green floatR marR" name="nextButton" value="" />
</div>
<div class="clear">
</div>
<% } %>
At the server side I use DataAnnotations attributes for validation.

Answer 1

the Button class has a CausesValidation property - if that is set to false, validation won't be triggered on postback.
Example:
<asp:Button id="btnCancel" CausesValidation="false" onClick="bntCancel_Click" Text="Cancel" runat="server" />
Note that this will disable the ASP.NET validators - if you have your own validation you will need to disable it another way.

Answer 2

Surround the text boxes with a form and turn next, back, and cancel into submit buttons. On event onsubmit, assign a method which returns true if the form is valid and should proceed to send it to the server, otherwise false.
So I would expect something along the lines of:
<form id="navigatorForm">
<!-- Various text forms here -->
<input type="submit" value="Back" onsubmit="back()" />
<input type="submit" value="Next" onsubmit="next()" />
<input type="submit" value="Cancel" onsubmit="cancel()" />
<input type="hidden" id="operation" name="operation" value="" />
</form>
<script type="text/javascript">
function validate() {
// Perform validation here
// If okay, return true, else false
}
function next() {
document.getElementById('operation').value = 'next';
if(!validate()) {
alert('Form is not filed correctly. Please pay more attention!');
return false; // Do not send to server!
} else {
return true;
}
}
function back() {
document.getElementById('operation').value = 'back';
return true;
}
function cancel() {
document.getElementById('operation').value = 'cancel';
return true;
}
</script>
Notice that unlike next(), back() and cancel() unconditionally return true, meaning that the request is sent to the server in any circumstance. At this point, on the server side, you'd need only to check to see if operation is next to know whether or not you should perform further testing.