A brief introduction of Fun in C# and its application to the project in combination with cache (local cache, Redis)

 1. A brief introduction to Fun

     Fun and Action in C# are somewhat similar, both are a delegate method, the difference is that Func has a return value, while Action does not.

 

    (T) The parameter types of the method this delegate encapsulates.

    Remarks: Learn more about Fun to ( https://www.cnblogs.com/LipeiNet/p/4694225.html )
      

  2. Simple example introduction
        This side defines a dictionary globally, encapsulates a method, defines two parameters as string type, and a delegate. Assuming that the calling method passes in a key, if there is a dictionary, it returns a Value, and if it does not, it returns the key through the delegation!
    Post a picture here to briefly introduce the code execution process
   

       2. Use in conjunction with cache encapsulation

      
       1). Get data
         

        /// <summary>
        /// retrieve data
        /// </summary>
        public void GetConfigsValue()
        {
            var key = "SysKeyInfo";
            var keyDic = GetDataLocalCache<string>(key, () =>
            {

                using (EntityContext db = new EntityContext())
                {
                    var value = db.Configs.FirstOrDefault(o => o.Name == "SysKeyInfo").Value;
                    return value;
                }

            }, DateTime.Now.AddHours(2));
        }

 

　　

 

       2). Get the cache

        

  /// <summary>
        /// Get cached data
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key">缓存key</param>
        /// <param name="callBack">Delegate method name</param>
        /// <param name="timeout">Cache expiration time</param>
        /// <returns></returns>
        public static T GetDataLocalCache<T>(string key, Func<T> callBack, DateTime? timeout = null)
        {
            if (!timeout.HasValue) timeout = DateTime.Now.AddMinutes(5);
            var cache = HttpRuntime.Cache [key];
            //If the cache does not exist or expires, execute the delegate method
            if (cache == null)
            {
                var result = callBack();
                if (result != null)
                    //Store the result of the delegate method execution in the cache
                    HttpRuntime.Cache.Insert(key, result, null, timeout.GetValueOrDefault(), System.Web.Caching.Cache.NoSlidingExpiration);
                return result;
            }
            else
            {
                return (T)cache;
            }
        }

 

　　

 

       3. Summary
       From the delegation of Func , we can see that it simplifies the tediousness of defining our own delegation, and at the same time it better combines the use of Lamdba . Reduced the role of custom functions. At the same time, there is also a disadvantage, that is, it is not easy to find where the error occurs. The use of Action delegate is the same as Func , so I won't talk about it here. I hope my summary can be helpful to you.
   
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