Is there a possibility to cache a collection, retrieved using WCF from an OData service.
The situation is the following:
I generated a WCF service client with Visual Studio 2015 using the metadata of the odata service. VS generated a class inheriting from System.Data.Services.Client.DataServiceContext. This class has some properties of type System.Data.Services.Client.DataServiceQuery<T>. The data of some of these properties change seldom. Because of performance reasons I want the WCF client to load these properties just the first time and not every time I use it in the code.
Is there a built in possibility to cache the data of these properties? Or can I tell the service client not to load specific proeprties newly every time.
Assuming the service client class is ODataClient and one of its properties is `Area, for now I get the values in the following way:
var client = new ODataClient("url_to_the_service");
client.IgnoreMissingProperties = true;
var propertyInfo = client.GetType().GetProperty("Area");
var area = propertyInfo.GetValue(client) as IEnumerable<object>;
The reason why I do this in such a complicated way is, that the client should be very generic: The properties to be handled can be configured in a configuration file.
* EDIT *
I already tried to find properties in the System.Data.Services.Client.DataServiceContext class or the System.Data.Services.Client.DataServiceQuery<T> class for the caching. But i wasn't able to find any.
To my knowledge there is no "out of the box" caching concept on the client. There are options for caching the output of a request on the server which is something you might want consider as well. Googling "WCF Caching" would get you a bunch of info on this.
Regarding client side caching...#Evk is correct it is pretty straight forward. Here is an sample using MemoryCache.
using System;
using System.Runtime.Caching;
namespace Services.Util
{
public class CacheWrapper : ICacheWrapper
{
ObjectCache _cache = MemoryCache.Default;
public void ClearCache()
{
MemoryCache.Default.Dispose();
_cache = MemoryCache.Default;
}
public T GetFromCache<T>(string key, Func<T> missedCacheCall)
{
return GetFromCache<T>(key, missedCacheCall, TimeSpan.FromMinutes(5));
}
public T GetFromCache<T>(string key, Func<T> missedCacheCall, TimeSpan timeToLive)
{
var result = _cache.Get(key);
if (result == null)
{
result = missedCacheCall();
if (result != null)
{
_cache.Set(key, result, new CacheItemPolicy { AbsoluteExpiration = DateTimeOffset.Now.Add(timeToLive) });
}
}
return (T)result;
}
public void InvalidateCache(string key)
{
_cache.Remove(key);
}
}
}
This is an example of code that uses the cache...
private class DataAccessTestStub
{
public const string DateTimeTicksCacheKey = "GetDateTimeTicks";
ICacheWrapper _cache;
public DataAccessTestStub(ICacheWrapper cache)
{
_cache = cache;
}
public string GetDateTimeTicks()
{
return _cache.GetFromCache(DateTimeTicksCacheKey, () =>
{
var result = DateTime.Now.Ticks.ToString();
Thread.Sleep(100); // Create some delay
return result;
});
}
public string GetDateTimeTicks(TimeSpan timeToLive)
{
return _cache.GetFromCache(DateTimeTicksCacheKey, () =>
{
var result = DateTime.Now.Ticks.ToString();
Thread.Sleep(500); // Create some delay
return result;
}, timeToLive);
}
public void ClearDateTimeTicks()
{
_cache.InvalidateCache(DateTimeTicksCacheKey);
}
public void ClearCache()
{
_cache.ClearCache();
}
}
And some tests if you fancy...
[TestClass]
public class CacheWrapperTest
{
private DataAccessTestStub _dataAccessTestClass;
[TestInitialize]
public void Init()
{
_dataAccessTestClass = new DataAccessTestStub(new CacheWrapper());
}
[TestMethod]
public void GetFromCache_ShouldExecuteCacheMissCall()
{
var original = _dataAccessTestClass.GetDateTimeTicks();
Assert.IsNotNull(original);
}
[TestMethod]
public void GetFromCache_ShouldReturnCachedVersion()
{
var copy1 = _dataAccessTestClass.GetDateTimeTicks();
var copy2 = _dataAccessTestClass.GetDateTimeTicks();
Assert.AreEqual(copy1, copy2);
}
[TestMethod]
public void GetFromCache_ShouldRespectTimeToLive()
{
_dataAccessTestClass.ClearDateTimeTicks();
var copy1 = _dataAccessTestClass.GetDateTimeTicks(TimeSpan.FromSeconds(2));
var copy2 = _dataAccessTestClass.GetDateTimeTicks();
Assert.AreEqual(copy1, copy2);
Thread.Sleep(3000);
var copy3 = _dataAccessTestClass.GetDateTimeTicks();
Assert.AreNotEqual(copy1, copy3);
}
[TestMethod]
public void InvalidateCache_ShouldClearCachedVersion()
{
var original = _dataAccessTestClass.GetDateTimeTicks();
_dataAccessTestClass.ClearDateTimeTicks();
var updatedVersion = _dataAccessTestClass.GetDateTimeTicks();
Assert.AreNotEqual(original, updatedVersion);
}
}
I have read lots of information about page caching and partial page caching in a MVC application. However, I would like to know how you would cache data.
In my scenario I will be using LINQ to Entities (entity framework). On the first call to GetNames (or whatever the method is) I want to grab the data from the database. I want to save the results in cache and on the second call to use the cached version if it exists.
Can anyone show an example of how this would work, where this should be implemented (model?) and if it would work.
I have seen this done in traditional ASP.NET apps , typically for very static data.
Here's a nice and simple cache helper class/service I use:
using System.Runtime.Caching;
public class InMemoryCache: ICacheService
{
public T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class
{
T item = MemoryCache.Default.Get(cacheKey) as T;
if (item == null)
{
item = getItemCallback();
MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(10));
}
return item;
}
}
interface ICacheService
{
T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class;
}
Usage:
cacheProvider.GetOrSet("cache key", (delegate method if cache is empty));
Cache provider will check if there's anything by the name of "cache id" in the cache, and if there's not, it will call a delegate method to fetch data and store it in cache.
Example:
var products=cacheService.GetOrSet("catalog.products", ()=>productRepository.GetAll())
Reference the System.Web dll in your model and use System.Web.Caching.Cache
public string[] GetNames()
{
string[] names = Cache["names"] as string[];
if(names == null) //not in cache
{
names = DB.GetNames();
Cache["names"] = names;
}
return names;
}
A bit simplified but I guess that would work. This is not MVC specific and I have always used this method for caching data.
I'm referring to TT's post and suggest the following approach:
Reference the System.Web dll in your model and use System.Web.Caching.Cache
public string[] GetNames()
{
var noms = Cache["names"];
if(noms == null)
{
noms = DB.GetNames();
Cache["names"] = noms;
}
return ((string[])noms);
}
You should not return a value re-read from the cache, since you'll never know if at that specific moment it is still in the cache. Even if you inserted it in the statement before, it might already be gone or has never been added to the cache - you just don't know.
So you add the data read from the database and return it directly, not re-reading from the cache.
For .NET 4.5+ framework
add reference: System.Runtime.Caching
add using statement:
using System.Runtime.Caching;
public string[] GetNames()
{
var noms = System.Runtime.Caching.MemoryCache.Default["names"];
if(noms == null)
{
noms = DB.GetNames();
System.Runtime.Caching.MemoryCache.Default["names"] = noms;
}
return ((string[])noms);
}
In the .NET Framework 3.5 and earlier versions, ASP.NET provided an in-memory cache implementation in the System.Web.Caching namespace. In previous versions of the .NET Framework, caching was available only in the System.Web namespace and therefore required a dependency on ASP.NET classes. In the .NET Framework 4, the System.Runtime.Caching namespace contains APIs that are designed for both Web and non-Web applications.
More info:
https://msdn.microsoft.com/en-us/library/dd997357(v=vs.110).aspx
https://learn.microsoft.com/en-us/dotnet/framework/performance/caching-in-net-framework-applications
Steve Smith did two great blog posts which demonstrate how to use his CachedRepository pattern in ASP.NET MVC. It uses the repository pattern effectively and allows you to get caching without having to change your existing code.
http://ardalis.com/Introducing-the-CachedRepository-Pattern
http://ardalis.com/building-a-cachedrepository-via-strategy-pattern
In these two posts he shows you how to set up this pattern and also explains why it is useful. By using this pattern you get caching without your existing code seeing any of the caching logic. Essentially you use the cached repository as if it were any other repository.
I have used it in this way and it works for me.
https://msdn.microsoft.com/en-us/library/system.web.caching.cache.add(v=vs.110).aspx
parameters info for system.web.caching.cache.add.
public string GetInfo()
{
string name = string.Empty;
if(System.Web.HttpContext.Current.Cache["KeyName"] == null)
{
name = GetNameMethod();
System.Web.HttpContext.Current.Cache.Add("KeyName", name, null, DateTime.Noew.AddMinutes(5), Cache.NoSlidingExpiration, CacheitemPriority.AboveNormal, null);
}
else
{
name = System.Web.HttpContext.Current.Cache["KeyName"] as string;
}
return name;
}
AppFabric Caching is distributed and an in-memory caching technic that stores data in key-value pairs using physical memory across multiple servers. AppFabric provides performance and scalability improvements for .NET Framework applications. Concepts and Architecture
Extending #Hrvoje Hudo's answer...
Code:
using System;
using System.Runtime.Caching;
public class InMemoryCache : ICacheService
{
public TValue Get<TValue>(string cacheKey, int durationInMinutes, Func<TValue> getItemCallback) where TValue : class
{
TValue item = MemoryCache.Default.Get(cacheKey) as TValue;
if (item == null)
{
item = getItemCallback();
MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(durationInMinutes));
}
return item;
}
public TValue Get<TValue, TId>(string cacheKeyFormat, TId id, int durationInMinutes, Func<TId, TValue> getItemCallback) where TValue : class
{
string cacheKey = string.Format(cacheKeyFormat, id);
TValue item = MemoryCache.Default.Get(cacheKey) as TValue;
if (item == null)
{
item = getItemCallback(id);
MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(durationInMinutes));
}
return item;
}
}
interface ICacheService
{
TValue Get<TValue>(string cacheKey, Func<TValue> getItemCallback) where TValue : class;
TValue Get<TValue, TId>(string cacheKeyFormat, TId id, Func<TId, TValue> getItemCallback) where TValue : class;
}
Examples
Single item caching (when each item is cached based on its ID because caching the entire catalog for the item type would be too intensive).
Product product = cache.Get("product_{0}", productId, 10, productData.getProductById);
Caching all of something
IEnumerable<Categories> categories = cache.Get("categories", 20, categoryData.getCategories);
Why TId
The second helper is especially nice because most data keys are not composite. Additional methods could be added if you use composite keys often. In this way you avoid doing all sorts of string concatenation or string.Formats to get the key to pass to the cache helper. It also makes passing the data access method easier because you don't have to pass the ID into the wrapper method... the whole thing becomes very terse and consistant for the majority of use cases.
Here's an improvement to Hrvoje Hudo's answer. This implementation has a couple of key improvements:
Cache keys are created automatically based on the function to update data and the object passed in that specifies dependencies
Pass in time span for any cache duration
Uses a lock for thread safety
Note that this has a dependency on Newtonsoft.Json to serialize the dependsOn object, but that can be easily swapped out for any other serialization method.
ICache.cs
public interface ICache
{
T GetOrSet<T>(Func<T> getItemCallback, object dependsOn, TimeSpan duration) where T : class;
}
InMemoryCache.cs
using System;
using System.Reflection;
using System.Runtime.Caching;
using Newtonsoft.Json;
public class InMemoryCache : ICache
{
private static readonly object CacheLockObject = new object();
public T GetOrSet<T>(Func<T> getItemCallback, object dependsOn, TimeSpan duration) where T : class
{
string cacheKey = GetCacheKey(getItemCallback, dependsOn);
T item = MemoryCache.Default.Get(cacheKey) as T;
if (item == null)
{
lock (CacheLockObject)
{
item = getItemCallback();
MemoryCache.Default.Add(cacheKey, item, DateTime.Now.Add(duration));
}
}
return item;
}
private string GetCacheKey<T>(Func<T> itemCallback, object dependsOn) where T: class
{
var serializedDependants = JsonConvert.SerializeObject(dependsOn);
var methodType = itemCallback.GetType();
return methodType.FullName + serializedDependants;
}
}
Usage:
var order = _cache.GetOrSet(
() => _session.Set<Order>().SingleOrDefault(o => o.Id == orderId)
, new { id = orderId }
, new TimeSpan(0, 10, 0)
);
public sealed class CacheManager
{
private static volatile CacheManager instance;
private static object syncRoot = new Object();
private ObjectCache cache = null;
private CacheItemPolicy defaultCacheItemPolicy = null;
private CacheEntryRemovedCallback callback = null;
private bool allowCache = true;
private CacheManager()
{
cache = MemoryCache.Default;
callback = new CacheEntryRemovedCallback(this.CachedItemRemovedCallback);
defaultCacheItemPolicy = new CacheItemPolicy();
defaultCacheItemPolicy.AbsoluteExpiration = DateTime.Now.AddHours(1.0);
defaultCacheItemPolicy.RemovedCallback = callback;
allowCache = StringUtils.Str2Bool(ConfigurationManager.AppSettings["AllowCache"]); ;
}
public static CacheManager Instance
{
get
{
if (instance == null)
{
lock (syncRoot)
{
if (instance == null)
{
instance = new CacheManager();
}
}
}
return instance;
}
}
public IEnumerable GetCache(String Key)
{
if (Key == null || !allowCache)
{
return null;
}
try
{
String Key_ = Key;
if (cache.Contains(Key_))
{
return (IEnumerable)cache.Get(Key_);
}
else
{
return null;
}
}
catch (Exception)
{
return null;
}
}
public void ClearCache(string key)
{
AddCache(key, null);
}
public bool AddCache(String Key, IEnumerable data, CacheItemPolicy cacheItemPolicy = null)
{
if (!allowCache) return true;
try
{
if (Key == null)
{
return false;
}
if (cacheItemPolicy == null)
{
cacheItemPolicy = defaultCacheItemPolicy;
}
String Key_ = Key;
lock (Key_)
{
return cache.Add(Key_, data, cacheItemPolicy);
}
}
catch (Exception)
{
return false;
}
}
private void CachedItemRemovedCallback(CacheEntryRemovedArguments arguments)
{
String strLog = String.Concat("Reason: ", arguments.RemovedReason.ToString(), " | Key-Name: ", arguments.CacheItem.Key, " | Value-Object: ", arguments.CacheItem.Value.ToString());
LogManager.Instance.Info(strLog);
}
}
I use two classes. First one the cache core object:
public class Cacher<TValue>
where TValue : class
{
#region Properties
private Func<TValue> _init;
public string Key { get; private set; }
public TValue Value
{
get
{
var item = HttpRuntime.Cache.Get(Key) as TValue;
if (item == null)
{
item = _init();
HttpContext.Current.Cache.Insert(Key, item);
}
return item;
}
}
#endregion
#region Constructor
public Cacher(string key, Func<TValue> init)
{
Key = key;
_init = init;
}
#endregion
#region Methods
public void Refresh()
{
HttpRuntime.Cache.Remove(Key);
}
#endregion
}
Second one is list of cache objects:
public static class Caches
{
static Caches()
{
Languages = new Cacher<IEnumerable<Language>>("Languages", () =>
{
using (var context = new WordsContext())
{
return context.Languages.ToList();
}
});
}
public static Cacher<IEnumerable<Language>> Languages { get; private set; }
}
I will say implementing Singleton on this persisting data issue can be a solution for this matter in case you find previous solutions much complicated
public class GPDataDictionary
{
private Dictionary<string, object> configDictionary = new Dictionary<string, object>();
/// <summary>
/// Configuration values dictionary
/// </summary>
public Dictionary<string, object> ConfigDictionary
{
get { return configDictionary; }
}
private static GPDataDictionary instance;
public static GPDataDictionary Instance
{
get
{
if (instance == null)
{
instance = new GPDataDictionary();
}
return instance;
}
}
// private constructor
private GPDataDictionary() { }
} // singleton
HttpContext.Current.Cache.Insert("subjectlist", subjectlist);
You can also try and use the caching built into ASP MVC:
Add the following attribute to the controller method you'd like to cache:
[OutputCache(Duration=10)]
In this case the ActionResult of this will be cached for 10 seconds.
More on this here
In an application there is a class that controls the cache of some data that is constantly reused.
We have had this code working for about a year, but lately, as the application (asp.net mvc 5) grows, it is throwing an error
Index was outside the bounds of the array when attempting to add more
data into it
It was fixed by restarting the IIS server.
How could we improve / modify this code to avoid the error?
public class DataCache
{
private static Dictionary<string, CacheEntry> _cacheEntries = new Dictionary<string, CacheEntry>();
public static bool Exists(string cacheId)
{
// Check if cache entry is valid.
if (_cacheEntries.ContainsKey(cacheId) && DateTime.UtcNow < _cacheEntries[cacheId].CacheUntil)
return true;
return false;
}
public static object Get(string cacheId)
{
// Return entry.
if (_cacheEntries.ContainsKey(cacheId))
return _cacheEntries[cacheId].Data;
else
return null;
}
public static void Put(object cacheObj, string cacheId, DateTime cacheUntil)
{
// Create new cache entry.
CacheEntry e = new CacheEntry()
{
Data = cacheObj,
CacheUntil = cacheUntil
};
// Delte pre-existing items.
if (_cacheEntries.ContainsKey(cacheId))
_cacheEntries.Remove(cacheId);
// Insert it into cache.
_cacheEntries.Add(cacheId, e);
}
class CacheEntry
{
public object Data;
public DateTime CacheUntil;
}
}
I use MemoryCache.Default instance of ObjectCache for storing data in MVC application; Every time I save some item and than immedeatly read it I see that items are stored as expected.But when new instance of Cashing class ( I mean class that used ObjectCache) is created I cant access old values.I have imlemented singleton for keeping only one instance for ObjectCache but this doesnt help me.
//here is single instance of caching object
public class CacheSingleton
{
private static CacheSingleton instance;
private CacheSingleton() { cache = MemoryCache.Default; }
public static CacheSingleton Instance
{
get
{
if (instance == null)
{
instance = new CacheSingleton();
}
return instance;
}
}
public ObjectCache cache { get; private set; }
}
// and here is piece of caching class
.........
private ObjectCache cache;
public DefaultCacheProvider()
{
cache = CacheSingleton.Instance.cache;
}
public object Get(string key)
{
return cache[key];
}
public void Set(string key, object data, int cacheTime, bool isAbsoluteExpiration)
{
CacheItemPolicy policy = new CacheItemPolicy();
if (isAbsoluteExpiration)
{
policy.AbsoluteExpiration = DateTime.Now + TimeSpan.FromMinutes(cacheTime);
}
else
{
policy.SlidingExpiration = TimeSpan.FromMinutes(cacheTime);
}
cache.Add(new CacheItem(key, data), policy);
}
public bool IsSet(string key)
{
return (cache[key] != null);
}
public void Invalidate(string key)
{
cache.Remove(key);
}
Can anybody explain why with every new instance of caching class (last code) I cant access old values.Thanks.
I would like to cache strings in memory from the database so that I do not have to access the database every time. I tried using System.Runtime.Caching, but it does not seem to work.
On the local site, all the data is cached but the user has to be authenticated on a secondary site. Once the user is authenticated, they are brought back to the local site but all the data that was cached is gone.
Is there a way to fix the above issue? Below is part of my code:
using System.Runtime.Caching;
ObjectCache cache = MemoryCache.Default;
public bool CacheIsSet(string key)
{
return cache.Contains(key);
}
public object CacheGet(string key)
{
return cache.Get(key);
}
public void CacheSet(string key, object value)
{
CacheItemPolicy policy = new CacheItemPolicy();
cache.Set(key, value, policy);
}
Thanks very much.
You should be referencing the HttpRuntime.Cache object. I created a wrapper around this, similar to what you have referenced in your question. Feel free to use it:
using System.Web.Caching;
public class CachingService
{
protected Cache Cache
{
get;
set;
}
public int CacheDurationMinutes
{
get;
set;
}
public CachingService()
{
Cache = HttpRuntime.Cache;
CacheDurationMinutes = 60;
}
public virtual object Get(string keyname)
{
return Cache[keyname];
}
public virtual T Get<T>(string keyname)
{
T item = (T)Cache[keyname];
return item;
}
public virtual void Insert(string keyname, object item)
{
Cache.Insert(keyname, item, null, DateTime.UtcNow.AddMinutes(CacheDurationMinutes), Cache.NoSlidingExpiration);
}
public virtual void Insert(string keyname, object item, CacheDependency dependency)
{
Cache.Insert(keyname, item, dependency);
}
public virtual void Remove(string keyname)
{
Cache.Remove(keyname);
}
}
Here is a sample use case. The function LoadPosts is supposed to load blog posts to display on the site. The function will first see if the posts are cached, if not it will load the posts from the database, and then cache them:
public IEnumerable<BlogPost> LoadPosts()
{
var cacheService = new CachingService();
var blogPosts = cacheService.Get<IEnumerable<BlogPost>>("BlogPosts");
if (blogPosts == null)
{
blogPosts = postManager.LoadPostsFromDatabase();
cacheService.Insert("BlogPosts", blogPosts);
}
return blogPosts;
}
The first time this function is run, the cache will return null, because we didn't add anything to the BlogPosts key yet. The second time the function is called the posts will be in the cache and the code in the if block will not run, saving us a trip to the database.