Why need use OnModelCreating (MVC 5 EF code first)?

Question

I don't understand what is the reason of using OnModelCreating function?

when I can do something like

[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Int Id { get; set; }

public Int LanguageId { get; set; }
[ForeignKey("LanguageId")]

public Language Language { get; set; }

Maybe I am wrong but when I reads about this,it is explained as it's for Many-to-Many relationship. so why not do something like this.

ICollection<User> Users

Rajput · Accepted Answer · 2016-12-01 11:55:24Z

5

For making relationship between entities, we have two options

DataAnnotation (Which you are using)
Fluent API.

When we are using fluent API we need to specify our relationship in this OnModelCreating(DbModelbuilder modelbuilder) method.So when model is created first time they should maintain relationship between entities.

Common Example for using this method is given in this below code snnipet

modelBuilder.Entity<Department>().Property(t => t.Name).HasMaxLength(50);

the same can be achieved using data annotation attribute.

[MaxLength(50)]
public string Name {get;set;}

So if you dont want to use DataAnotation Use Fluent API to serve your purpose.

edited Dec 1, 2016 at 11:55

answered Dec 1, 2016 at 11:48

Rajput

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