How to tell if any entities in context are dirty w

问题:

I want to be able to tell if there is any unsaved data in an entity framework context. I have figured out how to use the ObjectStateManager to check the states of existing entities, but there are two issues I have with this.

1. I would prefer a single function to call to see if any entities are unsaved instead of looping though all entities in the context.
2. I can't figure out how to detect entities I have added. This suggests to me that I do not fully understand how the entity context works. For example, if I have the ObjectSet myContext.Employees, and I add a new employee to this set (with .AddObject), I do not see the new entity when I look at the ObjectSet and I also don't see the .Count increase. However, when I do a context.SaveChanges(), my new entity is persisted...huh?

I have been unable to find an answer to this in my msdn searches, so I was hoping someone here would be able to clue me in.

Thanks in advance.

回答1:

var addedStateEntries = Context
    .ObjectStateManager
    .GetObjectStateEntries(EntityState.Added);

回答2:

Via extension method (for every ObjectContext):

internal static class ObjectContextExtensions
{
    public static bool IsContextDirty(this ObjectContext objectContext)
    {
        return objectContext
            .ObjectStateManager
            .GetObjectStateEntries(
                EntityState.Added | 
                EntityState.Deleted | 
                EntityState.Modified).Any();
    }
}

or via partial method (only for your ObjectContext):

partial class MyModel
{
    public bool IsContextDirty()
    {
        return ObjectStateManager
            .GetObjectStateEntries(
                EntityState.Added | 
                EntityState.Deleted |
                EntityState.Modified).Any();
    }
}

回答3:

A simple way to get a reusable single method/property you could add a new method to your ObjectContext by creating a partial class and adding a property like this:

public partial class MyEntityContext
{
  public bool IsContextDirty
  {
    get
    {
      var items = ObjectStateManager.GetObjectStateEntries(EntityState.Added);
      if(items.Any())
        return true;
      items = ObjectStateManager.GetObjectStateEntries(EntityState.Deleted);
      if (items.Any())
        return true;
      items = ObjectStateManager.GetObjectStateEntries(EntityState.Modified);
      if(items.Any())
        return true;
      return false;
    }
  }
}

Depending on what your looking for you could expose other properties to know if there are just deletes or modifications. This method could be simplified, but I wanted it to be clear what you would need to do.

回答4:

This article describes exactly what is needed to perform Change Tracking in the Entity Framework:

Identity Resolution, State Management, and Change Tracking (Entity Framework) - MSDN