Databento.Client 5.2.2

databento-dotnet

A high-performance .NET client for Databento market data. Stream real-time data or query historical records with async/await and IAsyncEnumerable.

Table of Contents

• Installation
• Quick Start
• Features
• Symbol Mapping
• Backtesting
• API Reference
• Building from Source
• Troubleshooting
• License

Installation

dotnet add package Databento.Client

Requirements: .NET 8.0 or .NET 9.0

Platforms: Windows x64 (NuGet package) | Linux/macOS (build from source)

Quick Start

1. Set Your API Key

# Windows
$env:DATABENTO_API_KEY="your-api-key"

# Linux/macOS
export DATABENTO_API_KEY="your-api-key"

Get your API key at databento.com/portal/keys

2. Live Streaming

using Databento.Client.Builders;
using Databento.Client.Models;

await using var client = new LiveClientBuilder()
    .WithKeyFromEnv()
    .WithAutoReconnect()  // Auto-reconnect on failure
    .Build();

// Live mode (requires market hours)
await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA" });

// Intraday Replay mode - replays from most recent market open, then continues live:
// (only available within 24h of last market open)
// await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA" },
//     startTime: DateTimeOffset.MinValue);

await client.StartAsync();

await foreach (var record in client.StreamAsync())
{
    if (record is TradeMessage trade)
        Console.WriteLine($"{trade.InstrumentId}: ${trade.PriceDecimal} x {trade.Size}");
}

3. Historical Data

using Databento.Client.Builders;
using Databento.Client.Models;

await using var client = new HistoricalClientBuilder()
    .WithKeyFromEnv()
    .Build();

var start = new DateTimeOffset(2025, 1, 15, 14, 30, 0, TimeSpan.Zero);
var end = start.AddHours(1);

await foreach (var record in client.GetRangeAsync(
    "EQUS.MINI", Schema.Trades, new[] { "NVDA" }, start, end))
{
    Console.WriteLine(record);
}

Features

Supported Schemas (20)

MBO · MBP-1 · MBP-10 · TBBO · Trades · OHLCV-1S · OHLCV-1M · OHLCV-1H · OHLCV-1D · OHLCV-EOD · Definition · Statistics · Status · Imbalance · CMBP-1 · CBBO-1S · CBBO-1M · TCBBO · BBO-1S · BBO-1M

Symbol Mapping

Records contain numeric InstrumentId values instead of ticker symbols. Resolve them as shown below.

Live Client Symbol Mapping

using System.Collections.Concurrent;
using Databento.Client.Builders;
using Databento.Client.Models;

var symbolMap = new ConcurrentDictionary<uint, string>();

await using var client = new LiveClientBuilder()
    .WithKeyFromEnv()
    .Build();

client.DataReceived += (sender, e) =>
{
    if (e.Record is SymbolMappingMessage mapping)
    {
        // Use STypeOutSymbol (NOT STypeInSymbol)
        symbolMap[mapping.InstrumentId] = mapping.STypeOutSymbol;
        Console.WriteLine($"Mapped {mapping.InstrumentId} to {mapping.STypeOutSymbol}");
        return;
    }

    if (e.Record is TradeMessage trade)
    {
        var symbol = symbolMap.GetValueOrDefault(trade.InstrumentId, "UNKNOWN");
        Console.WriteLine($"{symbol}: ${trade.PriceDecimal}");
    }
};

await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA", "AAPL" });
await client.StartAsync();
await foreach (var record in client.StreamAsync()) { }

Important: Always use STypeOutSymbol for the actual ticker. STypeInSymbol contains your subscription string (e.g., "ALL_SYMBOLS").

LiveBlocking Client Symbol Mapping

using System.Collections.Concurrent;
using Databento.Client.Builders;
using Databento.Client.Models;

var symbolMap = new ConcurrentDictionary<uint, string>();

await using var client = new LiveBlockingClientBuilder()
    .WithKeyFromEnv()
    .WithDataset("EQUS.MINI")
    .Build();

await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA", "AAPL" });
await client.StartAsync();

while (true)
{
    var record = await client.NextRecordAsync(timeout: TimeSpan.FromSeconds(5));
    if (record == null) break;

    if (record is SymbolMappingMessage mapping)
    {
        symbolMap[mapping.InstrumentId] = mapping.STypeOutSymbol;
        Console.WriteLine($"Mapped {mapping.InstrumentId} to {mapping.STypeOutSymbol}");
        continue;
    }

    if (record is TradeMessage trade)
    {
        var symbol = symbolMap.GetValueOrDefault(trade.InstrumentId, "UNKNOWN");
        Console.WriteLine($"{symbol}: ${trade.PriceDecimal}");
    }
}

Historical Client Symbol Mapping

Note: Historical API does not send SymbolMappingMessage. Use SymbologyResolveAsync() first.

using Databento.Client.Builders;
using Databento.Client.Models;

await using var client = new HistoricalClientBuilder()
    .WithKeyFromEnv()
    .Build();

var symbols = new[] { "NVDA", "AAPL" };
var start = new DateTimeOffset(2025, 1, 15, 14, 30, 0, TimeSpan.Zero);
var end = start.AddHours(1);

// Step 1: Resolve symbols to instrument IDs BEFORE streaming
var queryDate = DateOnly.FromDateTime(start.Date);
var resolution = await client.SymbologyResolveAsync(
    "EQUS.MINI", symbols, SType.RawSymbol, SType.InstrumentId,
    queryDate, queryDate.AddDays(1));

var symbolMap = new Dictionary<uint, string>();
foreach (var (inputSymbol, intervals) in resolution.Mappings)
    foreach (var interval in intervals)
        if (uint.TryParse(interval.Symbol, out var instrumentId))
        {
            symbolMap[instrumentId] = inputSymbol;
            Console.WriteLine($"Mapped {instrumentId} to {inputSymbol}");
        }

// Step 2: Stream data using the pre-built symbol map
await foreach (var record in client.GetRangeAsync(
    "EQUS.MINI", Schema.Trades, symbols, start, end))
{
    if (record is TradeMessage trade)
    {
        var symbol = symbolMap.GetValueOrDefault(trade.InstrumentId, "UNKNOWN");
        Console.WriteLine($"{symbol}: ${trade.PriceDecimal} x {trade.Size}");
    }
}

Backtesting

Run your trading strategies against historical data using the same code you use for live trading.

Historical API Backtesting

using Databento.Client.Builders;
using Databento.Client.Models;

var start = new DateTimeOffset(2025, 1, 15, 9, 30, 0, TimeSpan.FromHours(-5));
var end = start.AddHours(6.5);  // Full trading day

await using var client = new BacktestingClientBuilder()
    .WithKeyFromEnv()
    .WithTimeRange(start, end)
    .WithDiskCache()  // Cache for repeated runs
    .Build();

await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA", "AAPL" });
await client.StartAsync();

await foreach (var record in client.StreamAsync())
{
    if (record is TradeMessage trade)
        Console.WriteLine($"{trade.Timestamp}: {trade.PriceDecimal}");
}

File-Based Backtesting (Offline)

// No API key needed - use pre-downloaded DBN files
await using var client = new BacktestingClientBuilder()
    .WithFileSource("/path/to/historical_data.dbn")
    .Build();

await client.StartAsync();

await foreach (var record in client.StreamAsync())
{
    if (record is TradeMessage trade)
        Console.WriteLine($"{trade.PriceDecimal}");
}

Code Parity with Live Trading

// Your strategy works identically with live or backtest clients
async Task RunStrategy(ILiveClient client)
{
    await foreach (var record in client.StreamAsync())
    {
        if (record is TradeMessage trade)
            ProcessTrade(trade);
    }
}

// Backtest mode
await using var backtestClient = new BacktestingClientBuilder()
    .WithKeyFromEnv()
    .WithTimeRange(start, end)
    .Build();
await RunStrategy(backtestClient);

// Live mode - same strategy code!
await using var liveClient = new LiveClientBuilder()
    .WithKeyFromEnv()
    .Build();
await RunStrategy(liveClient);

See Backtesting Reference for playback control, caching options, and complete examples.

API Reference

LiveClient

await using var client = new LiveClientBuilder()
    .WithApiKey(apiKey)           // Or .WithKeyFromEnv()
    .WithDataset("GLBX.MDP3")     // Default dataset
    .WithAutoReconnect()          // Enable resilience
    .Build();

// Subscribe and stream
await client.SubscribeAsync(dataset, schema, symbols);
await client.StartAsync();
await foreach (var record in client.StreamAsync()) { }

// Events
client.DataReceived += (s, e) => { };
client.ErrorOccurred += (s, e) => { };

LiveBlockingClient

Pull-based API for explicit control over record retrieval:

await using var client = new LiveBlockingClientBuilder()
    .WithKeyFromEnv()
    .WithDataset("EQUS.MINI")
    .Build();

await client.SubscribeAsync("EQUS.MINI", Schema.Trades, new[] { "NVDA" });
await client.StartAsync();

// Pull records one at a time
while (true)
{
    var record = await client.NextRecordAsync(timeout: TimeSpan.FromSeconds(5));
    if (record == null) break;  // Timeout reached
    Console.WriteLine(record);
}

HistoricalClient

await using var client = new HistoricalClientBuilder()
    .WithKeyFromEnv()
    .Build();

await foreach (var record in client.GetRangeAsync(
    dataset, schema, symbols, startTime, endTime)) { }

ReferenceClient

var client = new ReferenceClientBuilder()
    .WithKeyFromEnv()  // Or .WithApiKey(apiKey)
    .Build();

// Security master
var records = await client.SecurityMaster.GetLastAsync(
    symbols: new[] { "NVDA" }, stypeIn: SType.RawSymbol);

// Adjustment factors
var adjustments = await client.AdjustmentFactors.GetRangeAsync(
    start: DateTimeOffset.UtcNow.AddDays(-90), symbols: new[] { "NVDA" });

// Corporate actions
var actions = await client.CorporateActions.GetRangeAsync(
    start: DateTimeOffset.UtcNow.AddYears(-1), symbols: new[] { "NVDA" });

Resilience & Auto-Reconnect

The client includes built-in resilience features for production deployments:

using Databento.Client.Builders;
using Databento.Client.Resilience;

await using var client = new LiveClientBuilder()
    .WithKeyFromEnv()
    .WithAutoReconnect()                              // Enable auto-reconnect
    .WithRetryPolicy(RetryPolicy.Aggressive)          // 5 retries, longer delays
    .WithHeartbeatTimeout(TimeSpan.FromSeconds(60))   // Stale connection detection
    .Build();

Retry Policies

Resilience Callbacks

using Databento.Client.Builders;
using Databento.Client.Resilience;

var options = new ResilienceOptions
{
    AutoReconnect = true,
    OnReconnecting = (attempt, ex) => {
        Console.WriteLine($"Reconnecting (attempt {attempt}): {ex.Message}");
        return true;  // Continue reconnecting
    },
    OnReconnected = (attempts) => Console.WriteLine($"Reconnected after {attempts} attempts"),
    OnReconnectFailed = (ex) => Console.WriteLine($"Reconnect failed: {ex.Message}")
};

await using var client = new LiveClientBuilder()
    .WithKeyFromEnv()
    .WithResilienceOptions(options)
    .Build();

Building from Source

Note: The NuGet package includes pre-built native libraries for Windows x64 only. Linux and macOS users must build from source.

Windows

# Prerequisites: .NET 8 SDK, CMake 3.24+, Visual Studio 2019+

# Full build (native + .NET)
.\build\build-all.ps1 -Configuration Release

# .NET only (if native library already built)
dotnet build -c Release

Linux

# Prerequisites
sudo apt-get update
sudo apt-get install -y cmake build-essential libssl-dev libzstd-dev

# Clone and build
git clone https://github.com/Alparse/databento-dotnet.git
cd databento-dotnet

# Build native library
./build/build-native.sh --configuration Release

# Build .NET
dotnet build -c Release

# Native library output: src/Databento.Interop/runtimes/linux-x64/native/libdatabento_native.so

macOS

# Prerequisites
brew install cmake openssl@3 zstd

# Clone and build
git clone https://github.com/Alparse/databento-dotnet.git
cd databento-dotnet

# Build native library
./build/build-native.sh --configuration Release

# Build .NET
dotnet build -c Release

# Native library output: src/Databento.Interop/runtimes/osx-*/native/libdatabento_native.dylib

Project Structure

databento-dotnet/
├── src/
│   ├── Databento.Client/     # High-level .NET API
│   ├── Databento.Interop/    # P/Invoke layer + runtimes/
│   └── Databento.Native/     # C++ wrapper (CMake)
├── examples/                  # 25+ working examples
└── docs/                      # Additional documentation

Troubleshooting

DllNotFoundException

The NuGet package includes native libraries for Windows x64 only.

On Windows:

1. Try dotnet restore --force
2. Install VC++ 2022 Redistributable

On Linux/macOS:

• You must build from source - native libraries are not included in the NuGet package

Connection Issues

// Enable logging for diagnostics
var client = new LiveClientBuilder()
    .WithKeyFromEnv()
    .WithLogger(loggerFactory.CreateLogger<ILiveClient>())
    .Build();

More Help

• AI Coding Agents Guide - Optimized reference for AI code agents
• API Reference - Quick-start guide with examples
• API Classification - Complete method signatures
• Databento Documentation
• Issue Tracker

License

Apache 2.0 - See LICENSE

Built on databento-cpp