# Switch to EF Core Oracle Provider

This document explains how to switch to the **Oracle** database provider for **[the application startup template](Startup-Templates/Application.md)** which comes with SQL Server provider pre-configured.

ABP Framework provides integrations for two Oracle packages:

* The [official Oracle NuGet package](https://www.nuget.org/packages/Oracle.EntityFrameworkCore) is free (**currently in beta**).
* [Devart](https://www.devart.com/) company has a [commercial (paid) NuGet package](https://www.nuget.org/packages/Devart.Data.Oracle.EFCore/).

> You can choose one of the package you want. If you don't know the differences of the packages, please search for it. ABP Framework only provides integrations we don't provide support for these 3rd-party libraries.

## Replace the Volo.Abp.EntityFrameworkCore.SqlServer Package

`.EntityFrameworkCore` project in the startup solution depends on the [Volo.Abp.EntityFrameworkCore.SqlServer](https://www.nuget.org/packages/Volo.Abp.EntityFrameworkCore.SqlServer) NuGet package. Remove this package and add the same version of one of the packages based on your preference;

* [Volo.Abp.EntityFrameworkCore.Oracle](https://www.nuget.org/packages/Volo.Abp.EntityFrameworkCore.Oracle) is the official and free package.
* [Volo.Abp.EntityFrameworkCore.Oracle.Devart](https://www.nuget.org/packages/Volo.Abp.EntityFrameworkCore.Oracle.Devart) is the paid Devart package.

### Replace the Module Dependency

Find ***YourProjectName*EntityFrameworkCoreModule** class inside the `.EntityFrameworkCore` project, remove `typeof(AbpEntityFrameworkCoreSqlServerModule)` from the `DependsOn` attribute. Then add one of the modules to the dependency list, based on the packages you've chosen:

* `typeof(AbpEntityFrameworkCoreOracleModule)` (official Oracle package). Also replace `using Volo.Abp.EntityFrameworkCore.SqlServer;` with `using Volo.Abp.EntityFrameworkCore.Oracle;`
* `typeof(AbpEntityFrameworkCoreOracleDevartModule)` (Devart package). Also replace `using Volo.Abp.EntityFrameworkCore.SqlServer;` with `using Volo.Abp.EntityFrameworkCore.Oracle.Devart;`

## UseOracle()

Find `UseSqlServer()` calls in your solution, replace with `UseOracle()`. Check the following files:

* *YourProjectName*EntityFrameworkCoreModule.cs inside the `.EntityFrameworkCore` project.
* *YourProjectName*MigrationsDbContextFactory.cs inside the `.EntityFrameworkCore.DbMigrations` project.


In the `CreateDbContext()` method of the *YourProjectName*MigrationsDbContextFactory.cs, replace the following code block

```csharp
var builder = new DbContextOptionsBuilder<YourProjectNameMigrationsDbContext>()
                .UseSqlServer(configuration.GetConnectionString("Default"));
```

with this one
```csharp
var builder = (DbContextOptionsBuilder<YourProjectNameMigrationsDbContext>)
	new DbContextOptionsBuilder<YourProjectNameMigrationsDbContext>().UseOracle
	(
		configuration.GetConnectionString("Default")
	);
```

> Depending on your solution structure, you may find more code files need to be changed.

## Change the Connection Strings

Oracle connection strings are different than SQL Server connection strings. So, check all `appsettings.json` files in your solution and replace the connection strings inside them. See the [connectionstrings.com]( https://www.connectionstrings.com/oracle/ ) for details of Oracle connection string options.

You typically will change the `appsettings.json` inside the `.DbMigrator` and `.Web` projects, but it depends on your solution structure.

## Re-Generate the Migrations

The startup template uses [Entity Framework Core's Code First Migrations](https://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/) by default. 
EF Core Migrations depend on the selected DBMS provider. Changing the DBMS provider, may not work with the existing migrations.

* Delete the `Migrations` folder under the `.EntityFrameworkCore.DbMigrations` project and re-build the solution.
* Run `Add-Migration "Initial"` on the Package Manager Console window (select the `.DbMigrator`  (or `.Web`) project as the startup project in the Solution Explorer and select the `.EntityFrameworkCore.DbMigrations` project as the default project in the Package Manager Console).

This will scaffold a new migration for Oracle.

Run the `.DbMigrator` project to create the database, apply the changes and seed the initial data.

## Run the Application

It is ready. Just run the application and enjoy coding.