Delete.ForeignKey("foreignkeyconstraint").OnTable("mytable");
        Delete.Index("UserId").OnTable("mytable");
        Rename.Column("UserId").OnTable("mytable").To("UserInfo_id");

Execute.Sql("EXEC sp_rename N'[Current_Primary_Key_Name]', '[New_Primary_Key_Name]', 'object';");

Delete.PrimaryKey("PRIMARY KEY").FromTable("mytable");