Devchain

Nethereum DevChain

DevChain is a complete in-process Ethereum node for .NET. It runs the full EVM (up to Prague), mines blocks instantly, and needs no external dependencies — no Docker, no Geth, no Hardhat, no Anvil.

When to Use This

• Running a local Ethereum node for development or testing
• Writing integration tests that need real EVM execution
• Replacing Hardhat or Anvil with a .NET-native solution
• Forking mainnet or L2s for local testing
• Debugging transaction execution at the opcode level
• Setting up Aspire-orchestrated dev environments

Packages

dotnet add package Nethereum.DevChain          # Core in-process node
dotnet add package Nethereum.DevChain.Server   # HTTP JSON-RPC server

Quick Start — In-Process Node

using Nethereum.DevChain;
using Nethereum.Web3;
using Nethereum.Web3.Accounts;

var account = new Account("0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80");
var devChain = new DevChainNode();
await devChain.StartAsync(account);  // Pre-funds with 10,000 ETH

var web3 = devChain.CreateWeb3(account);  // In-process, no HTTP

// Standard Nethereum APIs work as-is
var receipt = await web3.Eth.GetEtherTransferService()
    .TransferEtherAndWaitForReceiptAsync("0x70997970C51812dc3A010C7d01b50e0d17dc79C8", 1.0m);

devChain.Dispose();

Key Classes

Configuration

var config = new DevChainConfig
{
    ChainId = 1337,              // Default: 1337 (Hardhat preset: 31337)
    BlockGasLimit = 30_000_000,
    AutoMine = true,             // Mine instantly on each tx
    InitialBalance = BigInteger.Parse("10000000000000000000000")  // 10,000 ETH
};

var devChain = new DevChainNode(config);

Presets: DevChainConfig.Default (1337), DevChainConfig.Hardhat (31337), DevChainConfig.Anvil (31337).

Factory Methods

// One-liner
var devChain = await DevChainNode.CreateAndStartAsync(account);

// In-memory (no SQLite)
var devChain = DevChainNode.CreateInMemory();

// Multiple accounts
var devChain = new DevChainNode();
await devChain.StartAsync(alice, bob);
var accounts = await devChain.GenerateAndFundAccountsAsync(10);

Snapshot/Revert (Test Isolation)

var snapshot = await devChain.TakeSnapshotAsync();
// ... transactions ...
await devChain.RevertToSnapshotAsync(snapshot);  // Undo all changes

State Manipulation

await devChain.SetBalanceAsync(address, Web3.Convert.ToWei(1_000_000));
await devChain.SetNonceAsync(address, 100);
await devChain.SetCodeAsync(address, bytecode);
await devChain.SetStorageAtAsync(address, slot, value);

Via RPC: hardhat_setBalance, hardhat_setCode, hardhat_setNonce, hardhat_setStorageAt (also anvil_* aliases).

Forking

var config = new DevChainConfig
{
    ForkUrl = "https://eth.llamarpc.com",
    ForkBlockNumber = 19000000
};
var devChain = new DevChainNode(config);
await devChain.StartAsync(account);

CLI: nethereum-devchain -f https://eth.llamarpc.com --fork-block 19000000

Time Manipulation

devChain.DevConfig.AddTimeOffset(3600);           // Advance 1 hour
devChain.DevConfig.SetNextBlockTimestamp(1700000000); // Exact timestamp
await devChain.MineBlockAsync();

Debug Tracing

using Nethereum.CoreChain.Tracing;

var traceConfig = new OpcodeTraceConfig
{
    DisableMemory = true,
    DisableStack = false,
    DisableStorage = false
};

var trace = await devChain.TraceTransactionAsync(txHash, traceConfig);

HTTP Server (CLI)

nethereum-devchain                    # Defaults: port 8545, 10 accounts, auto-mine
nethereum-devchain -p 8546 -a 20     # Custom port and accounts
nethereum-devchain -f <url>          # Fork mode
nethereum-devchain --persist ./data  # Persistent storage

Embedding HTTP Server in ASP.NET

using Nethereum.DevChain.Server.Configuration;
using Nethereum.DevChain.Server.Hosting;
using Nethereum.DevChain.Server.Server;

var config = new DevChainServerConfig { ChainId = 31337, Storage = "memory" };
builder.Services.AddDevChainServer(config);
builder.Services.AddHostedService<DevChainHostedService>();

Integration Test Pattern

public class DevChainFixture : IAsyncLifetime
{
    public DevChainNode Node { get; private set; }
    public Account Alice { get; private set; }

    public async Task InitializeAsync()
    {
        Alice = new Account("0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80");
        Node = new DevChainNode(new DevChainConfig { ChainId = 31337 });
        await Node.StartAsync(Alice);
    }

    public Task DisposeAsync() { Node?.Dispose(); return Task.CompletedTask; }
}

// In test class: snapshot before each test, revert after
public async Task InitializeAsync() => _snapshot = await _fixture.Node.TakeSnapshotAsync();
public async Task DisposeAsync() => await _fixture.Node.RevertToSnapshotAsync(_snapshot);

Supported RPC Methods

Standard Ethereum (eth_*, net_*, web3_*), plus:

• Dev: evm_mine, evm_snapshot, evm_revert, evm_increaseTime, evm_setNextBlockTimestamp
• Hardhat: hardhat_setBalance, hardhat_setCode, hardhat_setNonce, hardhat_setStorageAt, hardhat_impersonateAccount, hardhat_stopImpersonatingAccount
• Anvil aliases: anvil_setBalance, anvil_setCode, anvil_setNonce, anvil_setStorageAt, anvil_mine, anvil_snapshot, anvil_revert
• Debug: debug_traceTransaction, debug_traceCall

Hardhat/Anvil Migration

Same default mnemonic (test test test test test test test test test test test junk), same derivation path (m/44'/60'/0'/0/{index}), same RPC methods, same chain ID (31337 with Hardhat/Anvil presets). Existing test scripts work without changes.

For full documentation, see: https://docs.nethereum.com/docs/devchain/overview