How can I stop Entity Framework 5 migrations addin

问题:

I started a project using Entity Framework 4.3 Code First with manual migrations and SQL Express 2008 and recently updated to EF5 (in VS 2010) and noticed that now when I change something like a foreign key constraint, the migrations code adds the "dbo." to the start of the table name and hence the foreign key name it constructs is incorrect for existing constraints (and in general now seem oddly named).

Original migration script in EF 4.3 (note ForeignKey("Products", t => t.Product_Id)):

    CreateTable(
        "Products",
        c => new
            {
                Id = c.Int(nullable: false, identity: true),
                ProductName = c.String(),
            })
        .PrimaryKey(t => t.Id);

    CreateTable(
        "KitComponents",
        c => new
            {
                Id = c.Int(nullable: false, identity: true),
                Component_Id = c.Int(),
                Product_Id = c.Int(),
            })
        .PrimaryKey(t => t.Id)
        .ForeignKey("Products", t => t.Component_Id)
        .ForeignKey("Products", t => t.Product_Id)
        .Index(t => t.Component_Id)
        .Index(t => t.Product_Id);

Foreign Key names generated: FK_KitComponents_Products_Product_Id FK_KitComponents_Products_Component_Id

If I then upgrade to EF5 and change the foreign key the migration code looks something like (note the "dbo.KitComponents" and "dbo.Products" as opposed to just "KitComponents" and "Products"):

DropForeignKey("dbo.KitComponents", "Product_Id", "dbo.Products");
DropIndex("dbo.KitComponents", new[] { "Product_Id" });

and the update-database fails with the message: 'FK_dbo.KitComponents_dbo.Products_Product_Id' is not a constraint. Could not drop constraint. See previous errors.

so it seems as of EF5 the constraint naming has changed from FK_KitComponents_Products_Product_Id to FK_dbo.KitComponents_dbo.Products_Product_Id (with dbo. prefix)

How can I get EF5 to behave as it was in EF 4.3 so I don't have to alter every piece of new migration code it spits out?

I haven't been able to find any release notes about why this changed and what to do about it :(

回答1:

You can customize the generated code by sub-classing the CSharpMigrationCodeGenerator class:

class MyCodeGenerator : CSharpMigrationCodeGenerator
{
    protected override void Generate(
        DropIndexOperation dropIndexOperation, IndentedTextWriter writer)
    {
        dropIndexOperation.Table = StripDbo(dropIndexOperation.Table);

        base.Generate(dropIndexOperation, writer);
    }

    // TODO: Override other Generate overloads that involve table names

    private string StripDbo(string table)
    {
        if (table.StartsWith("dbo."))
        {
            return table.Substring(4);
        }

        return table;
    }
}

Then set it in your migrations configuration class:

class Configuration : DbMigrationsConfiguration<MyContext>
{
    public Configuration()
    {
        CodeGenerator = new MyCodeGenerator();
    }
}

回答2:

For Automatic Migrations use this code:

public class MyOwnMySqlMigrationSqlGenerator : MySqlMigrationSqlGenerator
{
    protected override MigrationStatement Generate(AddForeignKeyOperation addForeignKeyOperation)
    {
        addForeignKeyOperation.PrincipalTable = addForeignKeyOperation.PrincipalTable.Replace("dbo.", "");
        addForeignKeyOperation.DependentTable = addForeignKeyOperation.DependentTable.Replace("dbo.", "");
        MigrationStatement ms = base.Generate(addForeignKeyOperation);
        return ms;
    }
}

And Set it on configuration:

SetSqlGenerator("MySql.Data.MySqlClient", new MyOwnMySqlMigrationSqlGenerator());

回答3:

This is a fine answer, however, if you're just looking for a 'quick fix' approach, there's this as well EF Migrations DropForeignKey fails when key is in a base class

Use the DropForeignKey overload which contains the parameters principalName and name -- which in this case means constraint name!

回答4:

Improving on bricelam's answer, I tried this on EF6. Made a few changes to keep the schema as part of table name and only remove it from the FK or PK name

internal class MyCodeGenerator : CSharpMigrationCodeGenerator
{
    protected override void Generate(AddForeignKeyOperation addForeignKeyOperation, IndentedTextWriter writer)
    {
        addForeignKeyOperation.Name = this.StripDbo(addForeignKeyOperation.Name, addForeignKeyOperation.DependentTable);
        addForeignKeyOperation.Name = this.StripDbo(addForeignKeyOperation.Name, addForeignKeyOperation.PrincipalTable);
        base.Generate(addForeignKeyOperation, writer);
    }

    protected override void Generate(AddPrimaryKeyOperation addPrimaryKeyOperation, IndentedTextWriter writer)
    {
        addPrimaryKeyOperation.Name = StripDbo(addPrimaryKeyOperation.Name, addPrimaryKeyOperation.Table);
        base.Generate(addPrimaryKeyOperation, writer);
    }

    protected override void Generate(DropForeignKeyOperation dropForeignKeyOperation, IndentedTextWriter writer)
    {
        dropForeignKeyOperation.Name = this.StripDbo(dropForeignKeyOperation.Name, dropForeignKeyOperation.DependentTable);
        dropForeignKeyOperation.Name = this.StripDbo(dropForeignKeyOperation.Name, dropForeignKeyOperation.PrincipalTable);
        base.Generate(dropForeignKeyOperation, writer);
    }

    protected override void Generate(DropPrimaryKeyOperation dropPrimaryKeyOperation, IndentedTextWriter writer)
    {
        dropPrimaryKeyOperation.Name = StripDbo(dropPrimaryKeyOperation.Name, dropPrimaryKeyOperation.Table);
        base.Generate(dropPrimaryKeyOperation, writer);
    }

    private string StripDbo(string objectName, string tableName)
    {
        if (tableName.StartsWith("dbo."))
        {
            return objectName.Replace(tableName, tableName.Substring(4));
        }

        return objectName;
    }
}