How to re-create database for Entity Framework

Question

I have got into a bad state with my ASP Net MVC 5 project  using Code-First Entity Framework  I don t care about losing data  I just want to be able to start fresh  recreate the database and start using Code-First migrations    Currently I am in a state where every attempt to Update-Database results in an exception being thrown or getting an error message  Also the website can t access the database correctly  How can I wipe all migrations  re-create the database and start from scratch without having to create a new project  In other words  I want to keep my code but drop the database   Later I will also want to get the deployment database  SQL Server on Azure  in sync  Again  I don t mind dropping all the data - I just want to get it working   Please provide any how-to steps to get back to a clean state  Much appreciated

User · Answer

Just want to add to the excellent answer of @Lin:

5) B. If you don't have SQL Management Studio, go to "SQL Server Object Explorer". If you cannot see your project db in the localdb "SQL Server Object Explorer", then click on "Add SQL server" button to add it to the list manually. Then you can delete the db from the list.

User · Answer

A possible very simple fix that worked for me  After deleting any database references and connections you find in server serverobject explorer  right click the App Data folder  didn t show any objects within the application for me  and select open  Once open put all the database etc  files in a backup folder or if you have the guts just delete them  Run your application and it should recreate everything from scratch

User · Answer

Follow below steps   1  First go to Server Explorer in Visual Studio  check if the   mdf  Data Connections for this project are   connected  if so  right click and delete   2  Go to Solution Explorer  click show All Files icon   3  Go to App Data  right click and delete all   mdf  files for this project   4  Delete Migrations folder by right click and delete   5  Go to SQL Server Management Studio  make sure the DB for this project is not there  otherwise delete it   6  Go to Package Manager Console in Visual Studio and type    Enable-Migrations -Force Add-Migration init Update-Database   7  Run your application  Note  In step 6 part 3  if you get an error  Cannot attach the file      it is possibly because you didn t delete the database files completely in SQL Server

User · Answer

I would like to add that Lin s answer is correct    If you improperly delete the MDF you will have to fix it  To fix the screwed up connections in the project to the MDF  Short answer  recreate and delete it properly    Create a new MDF and name it the same as the old MDF  put it in the same folder location   You can create a new project and create a new mdf  The mdf does not have to match your old tables  because were going to delete it  So create or copy an old one to the correct folder  Open it in server explorer  double click the mdf from solution explorer  Delete it in server explorer Delete it from solution explorer run update-database -force    Use force if necessary    Done  enjoy your new db  UPDATE 11 12 14  - I use this all the time when I make a breaking db change  I found this is a great way to roll back your migrations to the original db    Puts the db back to original  Run the normal migration to put it back to current   Update-Database -TargetMigration 0 -force   This will destroy all    tables and all data    Update-Database -force  use force if necessary

User · Answer

My solution is best suited for    - deleted your mdf file  - want to re-create your db   In order to recreate your database you need add the connection using Visual Studio   Step 1   Go to Server Explorer add new connection  or look for a add db icon    Step 2   Change Datasource to Microsoft SQL Server Database File   Step 3   add any database name you desire in the Database file name field  preferably the same name you have in the web config AttachDbFilename attribute   Step 4   click browse and navigate to where you will like it to be located   Step 5   in the package manager console run command update-database

User · Answer

While this question is premised by not caring about the data  sometimes maintenance of the data is essential   If so  I wrote a list of steps on how to recover from Entity Framework nightmare when the database already has tables with the same name here  How to recover from Entity Framework nightmare - database already has tables with the same name  Apparently    a moderator saw fit to delete my post so I ll paste it here   How to recover from Entity Framework nightmare - database already has tables with the same name  Description  If you re like us when your team is new to EF  you ll end up in a state where you either can t create a new local database or you can t apply updates to your production database  You want to get back to a clean EF environment and then stick to basics  but you can t  If you get it working for production  you can t create a local db  and if you get it working for local  your production server gets out of sync  And finally  you don t want to delete any production server data   Symptom  Can t run Update-Database because it s trying to run the creation script and the database already has tables with the same name      Error Message  System Data SqlClient SqlException  0x80131904   There   is already an object named    in the database    Problem Background  EF understands where the current database is at compared to where the code is at based on a table in the database called dbo   MigrationHistory  When it looks at the Migration Scripts  it tries to reconsile where it was last at with the scripts  If it can t  it just tries to apply them in order  This means  it goes back to the initial creation script and if you look at the very first part in the UP command  it ll be the CreeateTable for the table that the error was occurring on   To understand this in more detail  I d recommend watching both videos referenced here  https   msdn microsoft com en-us library dn481501 v vs 113  aspx  Solution  What we need to do is to trick EF into thinking that the current database is up to date while not applying these CreateTable commands  At the same time  we still want those commands to exist so we can create new local databases   Step 1  Production DB clean  First  make a backup of your production db  In SSMS  Right-Click on the database  Select  Tasks   Export Data-tier application     and follow the prompts  Open your production database and delete drop the dbo   MigrationHistory table   Step 2  Local environment clean Open your migrations folder and delete it  I m assuming you can get this all back from git if necessary   Step 3  Recreate Initial  In the Package Manager  run  Enable-Migrations   EF will prompt you to use -ContextTypeName if you have multiple contexts   Run  Add-Migration Initial -verbose   This will Create the initial script to create the database from scratch based on the current code  If you had any seed operations in the previous Configuration cs  then copy that across   Step 4  Trick EF At this point  if we ran Update-Database  we d be getting the original error  So  we need to trick EF into thinking that it s up to date  without running these commands  So  go into the Up method in the Initial migration you just created and comment it all out   Step 5  Update-Database With no code to execute on the Up process  EF will create the dbo   MigrationHistory table with the correct entry to say that it ran this script correctly  Go and check it out if you like  Now  uncomment that code and save  You can run Update-Database again if you want to check that EF thinks its up to date  It won t run the Up step with all of the CreateTable commands because it thinks it s already done this   Step 6  Confirm EF is ACTUALLY up to date If you had code that hadn t yet had migrations applied to it  this is what I did     Run  Add-Migration MissingMigrations  This will create practically an empty script  Because the code was there already  there was actually the correct commands to create these tables in the initial migration script  so I just cut the CreateTable and equivalent drop commands into the Up and Down methods   Now  run Update-Database again and watch it execute your new migration script  creating the appropriate tables in the database   Step 7  Re-confirm and commit  Build  test  run  Ensure that everything is running then commit the changes   Step 8  Let the rest of your team know how to proceed  When the next person updates  EF won t know what hit it given that the scripts it had run before don t exist  But  assuming that local databases can be blown away and re-created  this is all good  They will need to drop their local database and add create it from EF again  If they had local changes and pending migrations  I d recommend they create their DB again on master  switch to their feature branch and re-create those migration scripts from scratch

User · Answer

This worked for me    Delete database from SQL Server Object Explorer in Visual Studio  Right-click and select delete  Delete mdf and ldf files from file system - if they are still there  Rebuild Solution  Start Application - database will be re-created

[asp.net-mvc] How to re-create database for Entity Framework?

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