Devchain

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

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();

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);

// 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);

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

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);

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

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

using Nethereum.CoreChain.Tracing;

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

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

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

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>();

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);