entity-framework - SaveChanges 实际上调用了 DetectChanges 吗？

Question

我对 context.SaveChanges 是否会自动调用 DetectChanges 感到困惑。大多数有关 Entity Framework 的书籍和博客都说会。但我的简单代码片段。看起来 SaveChanges 没有调用 DetectChanges。

using (var context = new BreakAwayContext())
{
     context.Configuration.AutoDetectChangesEnabled = false;
     var grand = context.Destinations.Single(d => d.Name == "Grand Canyon");

     grand.Description = "Changed here";
     context.SaveChanges();                
}

这不会将更改的属性保存到数据库中。

这将:

using (var context = new BreakAwayContext())
{
     context.Configuration.AutoDetectChangesEnabled = false;
     var grand = context.Destinations.Single(d => d.Name == "Grand Canyon");

     grand.Description = "Changed here";
     context.ChangeTracker.DetectChanges();
     context.SaveChanges();                
}

非常感谢。

Answer 1

根据MSDN引用( https://msdn.microsoft.com/en-us/data/jj556205.aspx ) context.Configuration.AutoDetectChangesEnabled = false; 将停止发生自动更改检测，因此 context.SaveChanges(); 将不会保存任何更改。

正确的做法是:

context.Configuration.AutoDetectChangesEnabled = false;
//your changes starts
var grand = context.Destinations.Single(d => d.Name == "Grand Canyon");
grand.Description = "Changed here";
//your changes ends
context.Configuration.AutoDetectChangesEnabled = true; //enabling the auto detect
context.SaveChanges();

或者(你是如何做到的)

context.Configuration.AutoDetectChangesEnabled = false;
//your changes starts
var grand = context.Destinations.Single(d => d.Name == "Grand Canyon");
grand.Description = "Changed here";
//your changes ends
context.ChangeTracker.DetectChanges(); // manually ask for changes detection
context.SaveChanges();        

或者

不要将context.Configuration.AutoDetectChangesEnabled设置为false，除非它成为性能问题。