# Switch to EF Core Oracle Devart 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.

> This document uses a paid library of [Devart](https://www.devart.com/dotconnect/oracle/) company, See [this document](Entity-Framework-Core-Oracle.md) for other options.

> Before switching your provider, please ensure your Oracle version is **v12.2+**. In the earlier versions of Oracle, there were long identifier limitations that prevents creating a database table, column or index longer than 30 bytes. With [v12.2](https://docs.oracle.com/en/database/oracle/oracle-database/12.2/newft/new-features.html#GUID-64283AD6-0939-47B0-856E-5E9255D7246B) "The maximum length of identifiers is increased to 128 bytes". **v12.2** and later versions, you can use the database tables, columns and indexes provided by ABP without any problems. 

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

`.EntityFrameworkCore` project in the 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 the [Volo.Abp.EntityFrameworkCore.Oracle.Devart](https://www.nuget.org/packages/Volo.Abp.EntityFrameworkCore.Oracle.Devart) package.

## Replace the Module Dependency

Find ***YourProjectName*EntityFrameworkCoreModule** class inside the `.EntityFrameworkCore` project, remove `typeof(AbpEntityFrameworkCoreSqlServerModule)` from the `DependsOn` attribute, add `typeof(AbpEntityFrameworkCoreOracleDevartModule)`

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*DbContextFactory.cs inside the `.EntityFrameworkCore` project.


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

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

with this one
```csharp
var builder = (DbContextOptionsBuilder<YourProjectNameDbContext>)
	new DbContextOptionsBuilder<YourProjectNameDbContext>().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` 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` 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.