EF code first - custom foreign key constraint name

Question

I wonder if there is any chance to change name of foreign key constraint generated by Entity Framework when using code first.

I have two entities - User and Group - with many-to-many relationship so there is an association table GroupUser. Unfortunately, auto-generated foreign key constraints are named FK_dbo.GroupUser_dbo.User_User_UserId and FK_dbo.GroupUser_dbo.Group_Group_GroupId.

I would like to have foreign key constraints called like FK_GroupUser_UserId and FK_GroupUser_GroupId. That looks much cleaner to me.

Answer 1

It's not possible to customize the foreign key constraint name with data annotations or DbModelBuilder Fluent API. However, you can control the name with code-based migrations.

• First option: When the tables get created via migrations:

  The migration code that gets automatically generated for the join table would look like this:

  public partial class MyMigration : DbMigration
  {
      public override void Up()
      {
          CreateTable("GroupUser",
              c => new
              {
                  UserId = c.Int(nullable: false),
                  GroupId = c.Int(nullable: false),
              })
          .PrimaryKey(t => new { t.UserId, t.GroupId })
          .ForeignKey("User", t => t.UserId, cascadeDelete: true)
          .ForeignKey("Group", t => t.GroupId, cascadeDelete: true)
          .Index(t => t.UserId)
          .Index(t => t.GroupId);
  
          // ...
      }
  }
  

  Here you can modify the two ForeignKey method calls to set a custom constraint name before you call update-database:

          .ForeignKey("User", t => t.UserId, cascadeDelete: true,
              name: "FK_GroupUser_UserId")
          .ForeignKey("Group", t => t.GroupId, cascadeDelete: true,
              name: "FK_GroupUser_GroupId")
  

• Second option: When the tables already exist you can drop the constraint and add a new renamed one in a migration:

  public partial class MyMigration : DbMigration
  {
      public override void Up()
      {
          DropForeignKey("UserGroup", "UserId", "User");
          DropForeignKey("UserGroup", "GroupId", "Group");
  
          AddForeignKey("UserGroup", "UserId", "User",
              name: "FK_GroupUser_UserId");
          AddForeignKey("UserGroup", "GroupId", "Group",
              name: "FK_GroupUser_GroupId")
  
          // ...
      }
  }
  

Answer 2

You can implement a custom sql generator class derived from SqlServerMigrationSqlGenerator from System.Data.Entity.SqlServer

For more datail plese see the answer