Question

我有一个类跟这样的约束

public class product_new : NK.Objects._product_new
{
    private int Count_Per_Page;
    public product_new(int count_per_page)
    {
        this.Count_Per_Page = count_per_page;
    }
    public int CountOP///////count of pages
    {
        get
        {
            return number_of_pages(Count_Per_Page);
        }
    }

如您所见，CountOP返回一个int值，它连接到sql数据库以返回该值。

 private int number_of_pages(int tedad_per_pages)
 {
     return Q.Get_Back_Number_Of_Pages(
         tedad_per_pages, 
         tbl_name, 
         "", 
         new Queries.Cmd_Parameters());
 }

如果在这个类中创建对象，则在几次中不会更改CountOP，但会释放函数number_of_pages并连接到sql数据库。

如何缓存此变量？

Answer 1

引入一个私有后备字段，该字段保存值并在构造函数中初始化其值。现在，您可以在getter中返回变量值，而不是每次调用getter时都返回数据库。

public class product_new : NK.Objects._product_new
{
    private int Count_Per_Page;
    private readonly int _CountOP;

    public product_new(int count_per_page)
    {
        this.Count_Per_Page = count_per_page;
        this._CountOP = number_of_pages(count_per_page);
    }
    public int CountOP///////count of pages
    {
        get
        {
            return this._CountOP;
        }
    }

除此之外，我强烈建议您查看Mircrsofts naming-conventions。

Answer 2

尝试使用static Dictionary<int, int> - 一个字典来所有实例：

  public class product_new : NK.Objects._product_new {
    // Simplest, but not thread safe; use ConcurrentDictionary for thread safe version
    private static Dictionary<int, int> s_KnownAnswers = new Dictionary<int, int>();

    // Lazy: do not execute expensive operation eagerly: in the constructor;
    // but lazyly: in the property where we have to perform it
    public int CountOP {
      get {
        int result = 0;

        // do we know the answer? If yes, then just return it
        if (s_KnownAnswers.TryGetValue(Count_Per_Page, out result)) 
          return result;

        // if no, ask RDMBS
        result = number_of_pages(Count_Per_Page);

        // and store the result as known answer
        s_KnownAnswers.Add(Count_Per_Page, result); 

        return result;
      }
   }

    ...
  }

Answer 3

更改为使用支持的属性：

private int _npages = -1;
public int CountOP///////count of pages
    {
        get
        {
            if(_npages == -1)
                _npages = number_of_pages(Count_Per_Page);
            return _npages;
        } 
    }

在构造函数C＃中缓存varibale

3 个答案: