EntityFramework.Exceptions

If your application interacts with multiple different database types, use CompositeExceptionClassifier to wrap multiple specific classifiers. The composite classifier will iterate through its registered classifiers and return true if any of them identify the exception type.

var classifier = new CompositeExceptionClassifier(
    new PostgreSQLExceptionClassifier(),
    new SqlServerExceptionClassifier()
);

try
{
    await command.ExecuteNonQueryAsync();
}
catch (DbException ex) when (classifier.IsUniqueConstraintError(ex))
{
    // Works regardless of which database threw the exception
}

To enable the library, call the UseExceptionProcessor() extension method within your DbContext.OnConfiguring method.

class DemoContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseExceptionProcessor();
    }
}

class DemoContext : DbContext
{
    public DbSet<Product> Products { get; set; }
    public DbSet<ProductSale> ProductSale { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<Product>().HasIndex(u => u.Name).IsUnique();
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseExceptionProcessor();
    }
}

Install the specific NuGet package corresponding to your database provider to enable classification of provider-specific ADO.NET exceptions.

Supported providers include:

• PostgreSQL
• SQL Server
• SQLite
• Oracle
• MySQL (via DbExceptionClassifier.MySQL or DbExceptionClassifier.MySQL.Pomelo)

Note for SQLite users: If you want to use a custom native SQLite binary instead of e_sqlite3.dll, install the DbExceptionClassifier.Sqlite.Core package, which depends on Microsoft.Data.Sqlite.Core and does not bundle a native binary.

dotnet add package DbExceptionClassifier.PostgreSQL
dotnet add package DbExceptionClassifier.SqlServer
dotnet add package DbExceptionClassifier.Sqlite
dotnet add package DbExceptionClassifier.Oracle
dotnet add package DbExceptionClassifier.MySQL
dotnet add package DbExceptionClassifier.MySQL.Pomelo

Install the NuGet package that corresponds to your specific database provider to enable typed exception handling.

• SQL Server: dotnet add package EntityFrameworkCore.Exceptions.SqlServer
• MySQL: dotnet add package EntityFrameworkCore.Exceptions.MySQL
• MySQL (Pomelo): dotnet add package EntityFrameworkCore.Exceptions.MySQL.Pomelo
• PostgreSQL: dotnet add package EntityFrameworkCore.Exceptions.PostgreSQL
• SQLite: dotnet add package EntityFrameworkCore.Exceptions.Sqlite
• Oracle: dotnet add package EntityFrameworkCore.Exceptions.Oracle

If you are using AddDbContextPool, call UseExceptionProcessor() during the service registration instead of inside OnConfiguring. Replace the provider method (e.g., UseNpgsql) with your specific database provider.

builder.Services.AddDbContextPool<DemoContext>(options => options
    .UseNpgsql(config.GetConnectionString("DemoConnection"))
    .UseExceptionProcessor());

// Replace UseNpgsql with the sql flavor you're using
builder.Services.AddDbContextPool<DemoContext>(options => options
    .UseNpgsql(config.GetConnectionString("DemoConnection"))
    .UseExceptionProcessor());

If you are not using Entity Framework Core, you can use the DbExceptionClassifier packages to classify ADO.NET exceptions directly using the IDbExceptionClassifier interface. This approach has no EF Core dependency.

1. Install the provider-specific classifier (e.g., dotnet add package DbExceptionClassifier.PostgreSQL).
2. Use the classifier in a catch block with a when filter.

var classifier = new PostgreSQLExceptionClassifier();

try
{
    await command.ExecuteNonQueryAsync();
}
catch (DbException ex) when (classifier.IsUniqueConstraintError(ex))
{
    // Handle unique constraint violation
}

The IDbExceptionClassifier interface defines the contract for classifying DbException instances into common error categories. Implementations of this interface are provider-specific (e.g., SQL Server, PostgreSQL).

public interface IDbExceptionClassifier
{
    bool IsUniqueConstraintError(DbException exception);
    bool IsReferenceConstraintError(DbException exception);
    bool IsCannotInsertNullError(DbException exception);
    bool IsMaxLengthExceededError(DbException exception);
    bool IsNumericOverflowError(DbException exception);
    bool IsDeadlockError(DbException exception);
}