erc20

ERC-20 Tokens

Nethereum has a built-in typed service for ERC-20 — no ABI needed, no code generation. Just get the service for any token contract address and call methods directly. This is the simplest way to interact with fungible tokens.

NuGet: Nethereum.Web3

dotnet add package Nethereum.Web3

Get the Service

All ERC-20 operations start by getting a typed service for the token's contract address:

var erc20 = web3.Eth.ERC20.GetContractService(contractAddress);

Query Token Info

Every ERC-20 token exposes metadata. These are read-only calls — no gas, no signing needed:

var name = await erc20.NameQueryAsync();
var symbol = await erc20.SymbolQueryAsync();
var decimals = await erc20.DecimalsQueryAsync();
var totalSupply = await erc20.TotalSupplyQueryAsync();

The decimals value matters — ERC-20 tokens store balances as integers in the smallest unit. Most tokens use 18 decimals, but stablecoins like USDC use 6. Always use Web3.Convert.FromWei(value, decimals) to display human-readable amounts.

Check Balance

Balances are returned in the token's smallest unit. Use FromWei with the token's decimals for a readable value:

var balance = await erc20.BalanceOfQueryAsync(myAddress);
Console.WriteLine(
quot;Balance: {Web3.Convert.FromWei(balance, decimals)} {symbol}");

Transfer Tokens

Transfers require a Web3 instance connected with a funded account. The amount must be in the smallest unit — use ToWei with the token's decimals:

var receipt = await erc20.TransferRequestAndWaitForReceiptAsync(
    recipientAddress,
    Web3.Convert.ToWei(100, decimals));

Gas estimation, nonce, and EIP-1559 fees are handled automatically.

Approve and TransferFrom

The approve/transferFrom pattern lets another address (like a DEX or smart contract) spend your tokens. First approve a spending limit, then the spender calls transferFrom:

// Approve the spender
var approveReceipt = await erc20.ApproveRequestAndWaitForReceiptAsync(
    spenderAddress,
    Web3.Convert.ToWei(1000, decimals));

// Check allowance
var allowance = await erc20.AllowanceQueryAsync(myAddress, spenderAddress);

Be careful with approvals — approving a large amount gives the spender permission to transfer up to that amount at any time.

Listen for Transfer Events

ERC-20 transfers emit a Transfer event. Nethereum ships a built-in TransferEventDTO so you don't need to define your own:

using Nethereum.Contracts.Standards.ERC20.ContractDefinition;

var transferEvent = web3.Eth.GetEvent<TransferEventDTO>(contractAddress);
var filter = transferEvent.CreateFilterInput(
    BlockParameter.CreateEarliest(),
    BlockParameter.CreateLatest());

var transfers = await transferEvent.GetAllChangesAsync(filter);
foreach (var t in transfers)
{
    Console.WriteLine(
quot;{t.Event.From} -> {t.Event.To}: {Web3.Convert.FromWei(t.Event.Value, decimals)}");
}

Historical Queries

All query methods accept an optional BlockParameter to read state at a specific block. The node must have archive state for the requested block:

var historicalBalance = await erc20.BalanceOfQueryAsync(
    myAddress,
    new BlockParameter(15_000_000));

Available Methods

For full documentation, see: https://docs.nethereum.com/docs/smart-contracts/erc20