EF SaveChanges優化？

Question

爲什麼DbContext ctx在每個SaveChanges()執行後更快處置？

首先樣品：

var ctx = new DomainContext(); 
foreach (var item in deals) 
     { 
      DealsOfReutersAddition newDealAddition = 
         new DealsOfReutersAddition 
         { 
          DealsOfReutersId = item.DealsOfReutersId, 
          DealDate = DateTime.Parse(item.DateConfirmed ?? "01 01 01", new CultureInfo("en-US")), 
         }; 
      ctx.DealsOfReutersAdditions.Add(newDealAddition); 
      ctx.SaveChanges(); 
     } 

ctx.Dispose(); 

第二樣品：

foreach (var item in deals) 
     { 
      DealsOfReutersAddition newDealAddition = 
         new DealsOfReutersAddition 
         { 
          DealsOfReutersId = item.DealsOfReutersId, 
          DealDate = DateTime.Parse(item.DateConfirmed ?? "01 01 01", new CultureInfo("en-US")), 
         }; 
      var ctx = new DomainContext(); 
      ctx.DealsOfReutersAdditions.Add(newDealAddition); 
      ctx.SaveChanges(); 
      ctx.Dispose(); 
     } 

在1000行中第一估計8秒aganist 140秒第二樣品。 任何方式來清潔ctx，而不是重新創建？

Answer 1

沿着@JensKloster在評論中所說的話，你肯定不希望在循環中每一次都打電話SaveChanges。但我實際上會抵制把它放在循環之外的誘惑。由於上下文跟蹤的對象數量越來越多，更多的內存將用完，並且會使增量緩慢。

我對你的解決方案，那麼，就是在循環運行的計數器，以確定你會做保存：

int numberOfRecords = 0; 
using(var ctx = new DomainContext()) 
{ 
    foreach (var item in deals) 
      { 
       DealsOfReutersAddition newDealAddition = 
          new DealsOfReutersAddition 
          { 
           DealsOfReutersId = item.DealsOfReutersId, 
           DealDate = DateTime.Parse(item.DateConfirmed ?? "01 01 01", new CultureInfo("en-US")), 
          }; 

       ctx.DealsOfReutersAdditions.Add(newDealAddition); 

       numberOfRecords++; 
       if(numberOfRecords % 500 == 0) //Saves after every 500 rows. 
       { 
       ctx.SaveChanges(); 
       } 
      } 
}