泛型方法总是返回 NULL

Question

我的项目中有一个通用方法（已经由另一位开发人员开发）用于获取缓存；虽然我有键值，但方法仍然 returns NULL.

请看代码：

public static C GetFromCache<C>(string key) where C : class     
    {     
       if (cache != null)
       {
          var testCache = cache.Get(key); // This variable is getting results
          C p = cache.Get(key) as C; this point value of 'p' is NULL
          return p; 
        }

        return null;
    }

方法调用：

var lstCheck = ClassName.GetFromCache< List< int >(key);

Debugger screenshot

Answer 1

发生这种情况是因为 cache.Get(key) 的结果不是 C 类型 。让我用代码解释一下：

Object name = "my-name";
var nameAsString = name as String; // name is already a String, so nameAsString = "my-name"
var nameAsRandom = name as Random; // name isn't Random, so nameAsRandom == null

最佳，

泛型方法总是返回 NULL

Generic Method always returning NULL

c#

generics

caching

generic-method