Add-Migration does not detect the change for Entity Framwork in MVC project with Entity Framework 5

Question

I inherited this project which has been in Production for a long time and the original developer is no longer with the group. I needed to add a new column to one of the table in the database so I updated the object with a new column: public string status { get; set; }. and referenced it on a form. When published to IIS web server the project worked when published with Debug or QA configuration but not with Release configuration where the new column was not being referenced. It seems that the Entity Framework and the database is out of sync and I would need to run the Add-Migration and Update database commands. The issue I am seeing is that when I issue the Add-Migration command I got a file with lots of CreateTable in the up() method and lots of dropTable in the Down() method. I do not want to recreate the data since it is in the production for many years. So What did i do wrong? or What am I missing? How do i fix this?

Answer 1

Hi @Nguyen, David V ,
How exactly are you using migrations? This shouldn't be the case if you have migrations enabled and no initializers that drop and recreate the database.
You should have a backup, I recommend following the steps below to re-migrate.
Step 1: Models.cs

public string status { get; set; }  

Step 2: Models/ViewModels.cs

public string status { get; set; }  

Step 3: Views/***.cshtml
Add status input textbox to the view.

Step 4 :
Go to Tools > NuGet Manager > Package Manager Console

PM> Enable-Migrations  
PM> Add-Migration "status"  
PM> Update-Database  

EDIT

I am new to Entity Framework

I suggest you study the documentation, there are detailed steps in the documentation.
https://learn.microsoft.com/en-us/aspnet/mvc/overview/older-versions/hands-on-labs/aspnet-mvc-4-entity-framework-scaffolding-and-migrations#task-3--updating-the-database-using-entity-framework-migrations

the Migration folder is already in the DataAccess project/ add appropriate code to add Status column to the database

In this case, you can use Code First Migrations directly, open the Migrations\Configuration.cs file and add a new field. For specific steps, please refer to the following documents.
https://learn.microsoft.com/en-us/aspnet/mvc/overview/older-versions/getting-started-with-aspnet-mvc4/adding-a-new-field-to-the-movie-model-and-table#adding-a-rating-property-to-the-movie-model

What would Update-Database command do

Update-Database command applies migrations to the database.

From your description, you should not understand the Up() and Down() methods.
The Up() method upgrades your database from its current state (represented by your previous migrations) to the state expected by your current code migrations. The Down() method does the reverse - it removes all changes from the current migration and restores the database to the state expected by the previous migration. It's like installing/uninstalling migrations. When you call update-database, only one of these methods is executed. To use the Down method, you must explicitly specify the target migration for the upgrade. If the target migration is an older version, the migration API will automatically use the Down method and downgrade your database.

Best regards,
Lan Huang

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Answer 2

Thank you for your reply since I am really stuck at this point and don't know what to do.
I want to add when pulling the project from our source control server, the Migration folder is already in the DataAccess project and this folder contains a Configuration.cs and 2 other .cs files (201307310136475_CreateDataModel.cs and 201309231913222_revicacade.cs)

Yes I did all of these:

1. Added public string status { get; set; }' to the existing model
2. Enable-Migrations -ContextTypeName CustomerContext
   When issuing the Enable-Migrations I have to selected a specific context type because there are more than one context type in the project.
   This is what I got back:
   Migrations have already been enabled in project 'DataAccess'. To overwrite the existing migrations configuration, use the -Force parameter.
3. Add-Migrations Status
   This command created a 202210051450080_Status.cs file in the existing Migration folder.
   When open this file there are many CreateTable entries in the Up() method and there are many DropIndex, DropForeignKey and DropTable entries in the Down() method. I didn't want to proceed to the next command which is Update-Database because I think It would wipe out the tables and recreate new tables.
   This is where I don't know where or how to continue. Could I just delete the content of the Up() and Down() methods of the 02210051450080_Status.cs file and add appropriate code to add Status column to the database and then run the Update-Database command? What would Update-Database command do when there are a Configuration.cs and 3 other .cs files in the Migration folder? Sorry for so many question since I am new to Entity Framework since we don't normally used Entity Framework in our group.

Thank you in advance.