Question

I’m trying to implement the client-side caching of web service calls, and based on information from the web, I was able to do it according to the SetCachingPolicy() function as shown in code 1 below.

I was able to successfully get it working with a web method, RetrieveX, but not with method RetrieveY. I noticed that RetrieveX has no parameters and RetrieveY has one string parameter, and on inspection under Fiddler, the difference seems to be that the HTTP GET request of the web service call from RetrieveY has a query string for the parameter.

All HTTP GET web service calls so far without a query string is doing the caching properly, but not this call that has a query string in it.

Examination under Fiddler indicates that RetrieveX has the following caching information in output 1, and RetrieveY has the information in output 2.

Is this a limitation of this caching method or can I do something to get the client side caching of RetrieveY working?

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Code 1: SetCachingPolicy

private void SetCachingPolicy()
{
  HttpCachePolicy cache = HttpContext.Current.Response.Cache;
  cache.SetCacheability(HttpCacheability.Private);
  cache.SetExpires(DateTime.Now.AddSeconds((double)30));

  FieldInfo maxAgeField = cache.GetType().GetField(
      "_maxAge", BindingFlags.Instance | BindingFlags.NonPublic);
  maxAgeField.SetValue(cache, new TimeSpan(0, 0, 30));
}

Code 2: RetrieveX

[System.Web.Services.WebMethod]
[System.Web.Script.Services.ScriptMethod(UseHttpGet = true)]
public string[] RetrieveX()
{
  SetCachingPolicy();       
  // Implementation details here.
  return array;
}

Code 3: RetrieveY

[System.Web.Services.WebMethod]
[System.Web.Script.Services.ScriptMethod(UseHttpGet = true)]
public string[] RetrieveY(string arg1)
{
  SetCachingPolicy();       
  // Implementation details here.
  return array;
}

Output 1: RetrieveX caching info

HTTP/200 responses are cacheable by default, unless Expires, Pragma, or Cache-Control headers are present and forbid caching.
HTTP/1.0 Expires Header is present: Wed, 12 Sep 2012 03:16:50 GMT

HTTP/1.1 Cache-Control Header is present: private, max-age=30
    private: This response MUST NOT be cached by a shared cache.
    max-age: This resource will expire in .5 minutes. [30 sec]

Output 2: RetrieveY caching info

HTTP/200 responses are cacheable by default, unless Expires, Pragma, or Cache-Control headers are present and forbid caching.
HTTP/1.0 Expires Header is present: -1

Legacy Pragma Header is present: no-cache

HTTP/1.1 Cache-Control Header is present: no-cache
    no-cache: This response MUST NOT be reused without successful revalidation with the origin server.

Answer 1

I ran into this issue as well, I thought I’d share what worked for me. The underlying issue is that VaryByParams is not being set on the response. If you add this to your SetCachingPolicy() method RetrieveY should begin working as expected:

cache.VaryByParams["*"] = true