如何正确处理添加新项目到字典？ [英] How to correctly handle adding new item to dictionary?

问题描述

我有一个ASP.NET应用程序，我使用静态类作为缓存。在该静态类内部是内部字典，它保存缓存的对象。当然，静态类是Add / Remove / Clear ...的方法，如下所示：

  public static class CacheManager 
 {
私人静态字典< string，object> cacheItems = new Dictionary< string，object>（）; 
 
 private static ReaderWriterLockSlim locker = new ReaderWriterLockSlim（）; 
 
 public static Dictionary< string，object> CacheItems 
 {
 get 
 {
 return cacheItems; 
} 
} 
 
 public static void AddCacheItem（string key，object data）
 {
 locker.EnterWriteLock（）; 
 try 
 {
 cacheItems.Add（key，data）; 
} 
 finally 
 {
 locker.ExitWriteLock（）; 
} 
} 
 
 ... 
} 
  

当ASP.NET应用程序运行时，项目已添加到缓存（字典）中。我只是想问我应该检查例如Add方法，如果键已经以这种方式添加：

  public static void AddCacheItem （字符串键，对象数据）
 {
 locker.EnterWriteLock（）; 
 try 
 {
 if（！cacheItems.ContainsKey（key））
 {
 cacheItems.Add（key，data）; 
} 
} 
 finally 
 {
 locker.ExitWriteLock（）; 
} 
} 
  

或在第一个代码片段中保留它？ / p>

提前谢谢。

解决方案

您可以实现一种方法tryAdd

  public static bool TryAddCacheItem（string key，object data）
 {
 locker.EnterWriteLock（） ; 
 try 
 {
 if（cacheItems.ContainsKey（key））
 {
 return false; 
} 
 cacheItems.Add（key，data）; 
返回true; 
} 
 finally 
 {
 locker.ExitWriteLock（）; 
} 
} 
  

另外我建议使用 ConcurrentDictionary 。 这里是ConcurrentDictionary的代码。

I have an ASP.NET application where I use static class as cache. Inside that static class is internal dictionary, which holds cached objects. Of course, in static class are methods like Add/Remove/Clear... It looks as follows:

public static class CacheManager
{
    private static Dictionary<string, object> cacheItems = new Dictionary<string, object>();

    private static ReaderWriterLockSlim locker = new ReaderWriterLockSlim();

    public static Dictionary<string, object> CacheItems
    {
        get
        {
            return cacheItems;
        }
    }

    public static void AddCacheItem(string key, object data)
    {
        locker.EnterWriteLock();
        try
        {
            cacheItems.Add(key, data);
        }
        finally
        {
            locker.ExitWriteLock();
        }
    }

    ...
}

The items was added to the cache (dictionary) when ASP.NET application runs. I just want to ask should I check for example in Add method if key is already added in this way:

    public static void AddCacheItem(string key, object data)
    {
        locker.EnterWriteLock();
        try
        {
            if (!cacheItems.ContainsKey(key))
            {
                cacheItems.Add(key, data);
            }
        }
        finally
        {
            locker.ExitWriteLock();
        }
    }

Or leave it as is in first code snippet?

Thank you in advance.

解决方案

You can implement one more method TryAdd

public static bool TryAddCacheItem(string key, object data)
{
    locker.EnterWriteLock();
    try
    {
        if (cacheItems.ContainsKey(key))
        {
            return false;
        }
        cacheItems.Add(key, data);
        return true;
    }
    finally
    {
        locker.ExitWriteLock();
    }
}

Also I would suggest to use ConcurrentDictionary. Here is the code of the ConcurrentDictionary.

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