Define a field as autoincrement in EF5 migration - asp.net-mvc

Question

I'm creating a table using a EF migration such as:
this.CreateTable("Message",
c => new
{
Id = c.Long(nullable: false, identity: true, defaultValue: 0),
Subject = c.String(nullable: false, maxLength: 64),
Body = c.String(nullable: false, isMaxLength: true)
})
.PrimaryKey(c => c.Id)
.Index(c => c.Id, unique: true);
How can I define the Id field to be auto_increment? I'm pretty sure it has to be possible, but im just struggling to find out...
Thanks.

Answer 1

Ok, it seems that setting the property "identity: true" in field should be enough but for some reason the field is not defined as IDENTITY(1, 1).
Found a workaround in this post:
http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/33db16ac-e166-455f-a47b-1e5fe0557979/
And it worked for me like this:
Id = new ColumnModel(PrimitiveTypeKind.Int64) { IsNullable = false, IsIdentity = true },
Now its defining the column as IDENTITY(1, 1)

Answer 2

If you do want to automatically generate it in code, you could skip the annotation on the Id field and do something like below.
public abstract class AbstractContext : DbContext {
/// <summary>
/// Custom processing when saving entities in changetracker
/// </summary>
/// <returns></returns>
public override int SaveChanges()
{
// recommended to explicitly set New Guid for appropriate entities
foreach (var entry in ChangeTracker.Entries<ModelBase>().Where(e => e.State == EntityState.Added) ) {
// only generate if property isn't identity...
Type t = entry.Entity.GetType();
var info = t.GetProperty("Id").GetCustomAttributes(
typeof(DatabaseGeneratedAttribute), true).Cast<DatabaseGeneratedAttribute>().Single();
if (info.DatabaseGeneratedOption != DatabaseGeneratedOption.Identity) {
entry.Entity.Id = Guid.NewGuid(); // now we make it
}
}
return base.SaveChanges();
}
}
For more information check Working with Entity Keys
I got this from the link Which I showed above comment.
I hope this will help to you.