EF Code First - IsConcurrencyToken()

问题

Simple, but yet mysterious for me: Why do StringPropertyConfiguration (and all the other PropertyConfiguration) class(es) have 2 overloads for IsConcurrencyToken()?

The first:

public StringPropertyConfiguration IsConcurrencyToken()

Configures the property to be used as an optimistic concurrency token.

And the second:

public StringPropertyConfiguration IsConcurrencyToken(bool?)

Configures whether or not the property is to be used as an optimistic concurrency token.

Why would you use one over the other? As I see it, there's no difference at all between those two overloads (atleast not when working with them)...

By using the first you would write something like:

modelBuilder.Entity<Author>()
    .Property(x => x.Name)
    .IsConcurrencyToken();

And by using the second you would write:

modelBuilder.Entity<Author>()
    .Property(x => x.Name)
    .IsConcurrencyToken(true/false/null);

Have I missed something?

回答1:

My opinion...

The IsConcurrencyToken() defaults to true to provide a simple, fluent manner to define the entity.

The IsConcurrencyToken(bool?) allows the author to definitively set the ConcurrencyMode of the entity. This is useful for advanced scenarios:

Overriding the [ConcurrencyCheck] attribute on the POCO
Allowing a convention (removed in EF 4.1 RTW) to enable/disable the ConcurrencyMode based on some custom convention

Finally, I think IsConcurrencyToken(false) is better than IsNotConcurrencyToken().

来源：https://stackoverflow.com/questions/5980128/ef-code-first-isconcurrencytoken

标签

entity-framework

ef-code-first