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.

Try [how-to-customize-foreign-key-column...][1] [1]: http://stackoverflow.com/questions/5700645/how-to-customize-foreign-key-column-name-using-entity-framework-code-first — Nilesh, Jul 29 '13 at 14:23
That is only how to set custom column name not foreign key name. There is plenty of questions and answers on customizing foreign key column name but I didn't find any on customizing foreign name itself. — MrHenkey, Jul 29 '13 at 14:28

score 10 · Accepted Answer · answered Jul 29 '13 at 17:00

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")

        // ...
    }
}

How do I drop the foreign key if its already got a custom name, as the script generated uses the field names and so it doesnt get dropped because it doesnt enter the if statement — Alan Ball, Jul 20 '16 at 11:30
@AlanBall this is late, but to drop a foreign key with custom name, use DropForeignKey("TableName", "ForeignKeyName") — kitkatsim, Feb 21 '20 at 22:00

score 3 · Answer 2 · edited May 23 '17 at 12:22

3

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

For more datail plese see the answer

edited May 23 '17 at 12:22

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answered Jul 22 '15 at 21:02

Roman Marusyk

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EF code first - custom foreign key constraint name

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