Switch to EF Core Oracle Devart Provider

This document explains how to switch to the Oracle database provider for the application startup template which comes with SQL Server provider pre-configured.

This document uses a paid library of Devart company, See this document 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 "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 NuGet package. Remove this package and add the same version of the Volo.Abp.EntityFrameworkCore.Oracle.Devart package.

Replace the Module Dependency

Find YourProjectNameEntityFrameworkCoreModule 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:

• YourProjectNameEntityFrameworkCoreModule.cs inside the .EntityFrameworkCore project.
• YourProjectNameDbContextFactory.cs inside the .EntityFrameworkCore project.

In the CreateDbContext() method of the YourProjectNameDbContextFactory.cs, replace the following code block

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

with this one

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 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 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.

ORA-12899: value too large for column fix

Oracle limits strings to NVARCHAR2(2000) when the migration is created. Some of the entity properties may extend it. You can check the known and reported properties of ABP modules entities that can extend this limit. To prevent this problem, you need to convert the string type to long type first and generate a new migration. Then convert the long type to clob type with maximum length.

First Migration

Update you application DbContext OnModelCreating method:

protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        /* Include modules to your migration db context */

        builder.Entity<OpenIddictToken>(b =>
        {
            b.Property(q => q.Payload).HasColumnType("long").HasMaxLength(int.MaxValue);
        });
        
        builder.Entity<AuditLog>(b =>
        {
            b.Property(x => x.Exceptions).HasColumnType("long").HasMaxLength(int.MaxValue);
        });
        
        builder.Entity<AuditLogAction>(b =>
        {
            b.Property(x => x.Parameters).HasColumnType("long").HasMaxLength(int.MaxValue);
        });
        
        /* Configure your own tables/entities inside here */
    }

Create a new migration using dotnet tooling under EntityFrameworkCore layer of your solution: dotnet ef migrations add Oracle_Long_Conversion

Second Migration

Update you application DbContext OnModelCreating method:

protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        /* Include modules to your migration db context */

        builder.Entity<OpenIddictToken>(b =>
        {
            b.Property(q => q.Payload).HasColumnType("clob").HasMaxLength(4000);
        });
        
        builder.Entity<AuditLog>(b =>
        {
            b.Property(x => x.Exceptions).HasColumnType("clob").HasMaxLength(4000);
        });
        
        builder.Entity<AuditLogAction>(b =>
        {
            b.Property(x => x.Parameters).HasColumnType("clob").HasMaxLength(4000);
        });
        
        /* Configure your own tables/entities inside here */
    }

Create a new migration using dotnet tooling under EntityFrameworkCore layer of your solution: dotnet ef migrations add Oracle_Clob_Conversion

Run DbMigrator (or use dotnet tooling) to migrate the oracle database.

Run the Application

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