缓存在构造函数C＃

Question

的varibale我有一类constractor这样

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); 
     } 
    } 

你看到CountOP是返回一个int值，它是连接到SQL数据库返回该值。

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()); 
} 

在如果从这个类CountOP没有改变，但功能NUMBER_OF_PAGES创建对象几个时间被释放，并连接到SQL数据库。

我该如何缓存这个变量？

Answer 1

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

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 2

引入一个私有后台字段，它保存值并在构造函数中初始化它的值。现在，您可以在您的getter中返回变量值，而不是在每次调用getter时触击数据库。

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，我强烈建议看看Mircrsofts naming-conventions。

Answer 3

更改使用支持的房地产：

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