Entity Framework 4.1 code first approach: how to define length of properties

问题:

As the title implies:

how is it possible to tell Entity Framework 4.1 in code first approach, that i do want some properties (in particular of type string) to have a length of 256, or nvarchar(max), or...

So if this is for example my model

public class Book{    public string Title { get; set; } //should be 256 chars    public string Description {get;set} //should be nvarchar(max) } 

how could it be defined?

Thanks in advance!

回答1:

In EF4.1 RTW default length is nvarchar(max) for SQL Server and nvarchar(4000) for SQL CE. To change the length use either StringLength or MaxLength annotations or fluent mapping HasMaxLength:

[StringLength(256)] public string Title { get; set; } 

Or

[MaxLength(256)] public string Title { get; set; } 

Or

modelBuilder.Entity<Book>()             .Property(p => p.Title)             .HasMaxLength(256); 

回答2:

As is stated in my comment, it's simple.
Just use [StringLength(1000)] or [MaxLength] from DataAnnotation.

文章来源: Entity Framework 4.1 code first approach: how to define length of properties