Léger

Léger is a lightweight library that aims to make working with ADO.NET from C# a lot simpler. Functionality is delivered through a multifaceted API that bears a resemblance to Dapper with a focus on manual mapping and a few extra goodies built-in.

Key Features

• No reflection, no magic, no surprises.
• Simple and uniform execution model, delivered as IDbConnection, IDbCommand, IDbTransaction and IDbConnectionFactory extension methods.
• Safe value reading via IDataRecord and IDataReader extensions.
• Enhanced exception output.
• Async versions of all data access methods.

Design Goals

• Augment the base ADO.NET functionality as little as possible and adhering to internal naming conventions.
• Encourage manual mappings by providing a succinct and safe methodology to obtain values from tabular data.
• Provide an easy to reason about execution model.
• Support asynchronous database workflows.

Getting Started

Install the Leger NuGet package:

PM>  Install-Package Leger

Or using the dotnet CLI

dotnet add package Leger

Quick Start

using System;
using System.Data.Sqlite;
using Leger;

using var connection = new SqliteConnection("{your connection string}");

var books = connection.Query("""
    SELECT name FROM book WHERE author_id = @author_id"
    """,
    new("author_id", 1),
    rd => rd.ReadString("name"));

foreach(var book in books)
{
    Console.WriteLine(book);
}

An Example using SQLite

For this example, assume we have an IDbConnection named connection:

using var connection = new SqliteConnection("Data Source=author.db");

With the following database schema:

CREATE TABLE author (
    author_id INTEGER PRIMARY KEY,
    full_name TEXT);

And domain model:

public record Author(
    int AuthorId,
    string FullName);

public static class AuthorReader
{
    public static Author Map(IDataReader rd) =>
        new(AuthorId = rd.ReadInt32("author_id"),
            FullName = rd.ReadString("full_name"));
}

Query for multiple strongly-type results

var authors = connection.Query("""
    SELECT author_id, full_name FROM author
    """,
    AuthorReader.Map);

// async
var authors = await connection.QueryAsync("""
    SELECT author_id, full_name FROM author
    """,
    AuthorReader.Map);

Query for a single strongly-type result

// `QuerySingle` is optimized to dispose the `IDataReader` after safely reading the first `IDataRecord`.
var author = connection.QuerySingle("""
    SELECT author_id, full_name FROM author WHERE author_id = @author_id
    """,
    new("author_id", authorId),
    AuthorReader.Map);

// async
var author = await connection.QuerySingleAsync("""
    SELECT author_id, full_name FROM author WHERE author_id = @author_id
    """,
    new("author_id", authorId),
    AuthorReader.Map);

Execute a statement

connection.Execute("""
    INSERT INTO author (full_name) VALUES (@full_name)
    """,
    new("full_name", "John Doe"));

// async
await connection.ExecuteAsync("""
    INSERT INTO author (full_name) VALUES (@full_name)
    """,
    new("full_name", "John Doe"));

Execute a statement multiple times

public record NewAuthor(
    string FullName);

IEnumerable<NewAuthor> newAuthors = [new("John Doe"), new("Jane Doe")];

connection.ExecuteMany("""
    INSERT INTO author (full_name) VALUES (@full_name)
    """,
    newAuthors.Select(a => new DbParams("full_name", a.FullName)));

// async
await connection.ExecuteManyAsync("""
    INSERT INTO author (full_name) VALUES (@full_name)
    """,
    newAuthors.Select(a => new DbParams("full_name", a.FullName)));

Execute a statement transactionally

using var transaction = connection.CreateTransaction();

transaction.Execute("""
    UPDATE author SET full_name = @full_name where author_id = @author_id
    """,
    new(){
        { "author_id", author.AuthorId },
        { "full_name", author.FullName }
    });

transaction.Commit();

Execute a scalar command (single value)

var count = connection.Scalar("""
    SELECT COUNT(*) AS author_count FROM author
    """,
    new("full_name", "John Doe"));

// async
var count = await connection.ScalarAsync("""
    SELECT COUNT(*) AS author_count FROM author
    """,
    new("full_name", "John Doe"));

IDbConnectionFactory

The IDbConnectionFactory interface is provided to allow for the creation of IDbConnection instances. This is useful when you want to abstract the creation of connections and even moreso in multi-data source scenarios.

Implementing the interface is straightforward, an example using System.Data.Sqlite is shown below:

public class SqliteConnectionFactory(connectionString)
    : IDbConnectionFactory
{
    public IDbConnection CreateConnection() =>
        new SqliteConnection(connectionString);
}

The expectation is that the connection is left closed, and the API methods will open and close the connection as needed.

IDataRecord Extension Methods

To make obtaining values from IDataRecord more straight-forward, 2 sets of extension methods are available for:

• Get value, automatically defaulted
• Get value as Nullable<'a>

Assume we have an active IDataRecord called `rd and are currently reading a row, the following extension methods are available to simplify reading values:

public static string ReadString(this IDataRecord rd, string field);
public static char ReadChar(this IDataRecord rd, string field);
public static bool ReadBoolean(this IDataRecord rd, string field);
public static bool ReadBool(this IDataRecord rd, string field);
public static byte ReadByte(this IDataRecord rd, string field);
public static short ReadInt16(this IDataRecord rd, string field);
public static short ReadShort(this IDataRecord rd, string field);
public static int ReadInt32(this IDataRecord rd, string field);
public static int ReadInt(this IDataRecord rd, string field);
public static int ReadInt(this IDataRecord rd, string field);
public static long ReadInt64(this IDataRecord rd, string field);
public static long ReadLong(this IDataRecord rd, string field);
public static decimal ReadDecimal(this IDataRecord rd, string field);
public static double ReadDouble(this IDataRecord rd, string field);
public static float ReadFloat(this IDataRecord rd, string field);
public static Guid ReadGuid(this IDataRecord rd, string field);
public static DateTime ReadDateTime(this IDataRecord rd, string field);
public static byte[] ReadBytes(this IDataRecord rd, string field);

public static bool? ReadNullableBoolean(this IDataRecord rd, string field);
public static bool? ReadNullableBool(this IDataRecord rd, string field);
public static byte? ReadNullableByte(this IDataRecord rd, string field);
public static short? ReadNullableInt16(this IDataRecord rd, string field);
public static short? ReadNullableShort(this IDataRecord rd, string field);
public static int? ReadNullableInt32(this IDataRecord rd, string field);
public static int? ReadNullableInt(this IDataRecord rd, string field);
public static int? ReadNullableInt(this IDataRecord rd, string field);
public static long? ReadNullableInt64(this IDataRecord rd, string field);
public static long? ReadNullableLong(this IDataRecord rd, string field);
public static decimal? ReadNullableDecimal(this IDataRecord rd, string field);
public static double? ReadNullableDouble(this IDataRecord rd, string field);
public static float? ReadNullableFloat(this IDataRecord rd, string field);
public static Guid? ReadNullableGuid(this IDataRecord rd, string field);
public static DateTime? ReadNullableDateTime(this IDataRecord rd, string field);

Errors and Exceptions

Leger provides enhanced exception output to help you quickly identify and resolve issues. The following exceptions are thrown:

• DatabaseExecutionException
  • Thrown when an error occurs during the execution of a command.
  • Includes the SQL statement that was executed,
  • Or, the field name and value that caused the error.
• DatabaseConnectionException - thrown when a connection cannot be established.
• DatabaseTransactionException - thrown when an error occurs during a transaction.

Contribute

Thank you for considering contributing to Leger, and to those who have already contributed! We appreciate (and actively resolve) PRs of all shapes and sizes.

We kindly ask that before submitting a pull request, you first submit an issue or open a discussion.

If functionality is added to the API, or changed, please kindly update the relevant document. Unit tests must also be added and/or updated before a pull request can be successfully merged.

Only pull requests which pass all build checks and comply with the general coding guidelines can be approved.

If you have any further questions, submit an issue or open a discussion.

License

Built with ♥ by Pim Brouwers in Toronto, ON. Licensed under MIT.