Question
I'm trying understand the basics of Entity Framework and I have a question about the Set<> method on DbContext. I am using a database first model for the following question.
Let's say I have an ActivityLog database which amongst other things I can use to pull out a message (NLog message, for example). I could write some code to pull out all messages like this:
using (var entities = new ActivityLogEntities())
foreach (var log in entities.AcitivityLogs)
Console.WriteLine(log.Message);
However I could also achieve the same thing doing this:
using (var entities = new ActivityLogEntities())
foreach (var message in entities.Set<ActivityLog>().Select(entity => entity.Message))
Console.WriteLine(message);
My question is what is the difference between these two statements? When is it more appropriate to use one over the other? Or is this just a matter of personal preference?
Accepted Answer
There's no significant difference. In the first case, you have something like:
class MyContext : DbContext
{
public DbSet<AcitivityLog> AcitivityLogs { get; set; }
}
When context is creating, it looks for public DbSet<T> read/write-properties, and does this (pseudo-code):
dbSetProperty = Set<EntityType>();
But, there are cases, when you:
1) don't want to make public properties for all of you entity types;
2) don't know all of the entity types at context's design time.
In these cases Set<T> is the only way to get proper entity set.
Popular Answer
The only reason i have ever used Set<T> is when you are acting on a type you dont know, eg a generic insert.
Heres an example from my generic repository:
public void AddOnSave(T entity)
{
ctx.Set<T>.Add(entity);
}
Using it for regular stuff just makes the code less readable IMHO
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