How to prevent web service results from being cached in an ASP.NET web service?

Question

In my ASP.NET app, I noticed that the results of any web service calls are cached. I don't want any results to be cached, how can I stop the browser from caching the results?

Update:

Here's the proxy code generated by calling the web service URL appending '/js', e.g. /mywebservice.asmx/js

var MyWebService=function() {
MyWebService.initializeBase(this);
this._timeout = 0;
this._userContext = null;
this._succeeded = null;
this._failed = null;
}
MyWebService.prototype={
SomeWebMethod:function(itemID,succeededCallback, failedCallback, userContext) {
return this._invoke(MyWebService.get_path(), 'SomeWebMethod',false,
{itemID:itemID},succeededCallback,failedCallback,userContext); }}
MyWebService.registerClass('MyWebService',Sys.Net.WebServiceProxy);
MyWebService._staticInstance = new MyWebService();
MyWebService.set_path = function(value) { MyWebService._staticInstance._path = value; }
MyWebService.get_path = function() { return MyWebService._staticInstance._path; }
MyWebService.set_timeout = function(value) { MyWebService._staticInstance._timeout = value; }
MyWebService.get_timeout = function() { return MyWebService._staticInstance._timeout; }
MyWebService.set_defaultUserContext = function(value) { MyWebService._staticInstance._userContext = value; }
MyWebService.get_defaultUserContext = function() { return MyWebService._staticInstance._userContext; }
MyWebService.set_defaultSucceededCallback = function(value) { MyWebService._staticInstance._succeeded = value; }
MyWebService.get_defaultSucceededCallback = function() { return MyWebService._staticInstance._succeeded; }
MyWebService.set_defaultFailedCallback = function(value) { MyWebService._staticInstance._failed = value; }
MyWebService.get_defaultFailedCallback = function() { return MyWebService._staticInstance._failed; }
MyWebService.set_path("/MyWebService.asmx");
MyWebService.SomeWebMethod= function(itemID,onSuccess,onFailed,userContext)
{MyWebService._staticInstance.SomeWebMethod(itemID,onSuccess,onFailed,userContext); }

I call the service using:

MyWebService.SomeWebMethod(
itemID,
function(sender, e)
 {
    // do something
},
function(sender, e)
{
   // handle failure
});

I use the suggested technique (append a param to the URL with some random value) with others pages to prevent them from being cached, but I'm surprised that I need to use this technique with a web service call considering that they are POST calls by default in ASP.NET 2.0 and shouldn't be cached in the first place.

Answer 1

When you make a request to a web service, append a unique value to the querystring, such as the current date and time converted to a numeric value, this will ensure that it's treated as a unique request each time and no caching of responses will take place.

Specifically the Javscript Date.getTime() method:

var d = new Date();
var uniqueValue = d.getTicks();

// Now append uniqueValue to the querystring you're calling the webservice with
// and it'll ensure the request is treated as unique by the browsers cache

Answer 2

how can I stop the browser from caching the results?

Could it be that you're using ASP.NET ajax? If so then I think you mean that the ajax calls get cached by the browser. If so then take a look at this: http://yoavniran.wordpress.com/2010/04/27/ie-caching-ajax-results-how-to-fix/.

Answer 3

If you have control over the server, look here for IIS7

On older versions of IIS add a

Cache-Control: no-cache 

to the headers for the ASMX / SVC file (or for the whole directory)

Answer 4

I guess you are using IE... is a pita regarding cache control.

The cache-control header can be managed on a request by request basis by using the response object. Be aware that you can't modify the response header once you have issued the first byte of response body.