Built In Standards

ERC-20: Fungible Tokens

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

var name = await erc20.NameQueryAsync();
var symbol = await erc20.SymbolQueryAsync();
var decimals = await erc20.DecimalsQueryAsync();
var totalSupply = await erc20.TotalSupplyQueryAsync();
var balance = await erc20.BalanceOfQueryAsync(ownerAddress);
var allowance = await erc20.AllowanceQueryAsync(owner, spender);

// Transfer
var receipt = await erc20.TransferRequestAndWaitForReceiptAsync(to, amount);

ERC-721: NFTs

var erc721 = web3.Eth.ERC721.GetContractService(nftAddress);

var name = await erc721.NameQueryAsync();
var symbol = await erc721.SymbolQueryAsync();
var balance = await erc721.BalanceOfQueryAsync(ownerAddress);
var owner = await erc721.OwnerOfQueryAsync(tokenId);
var tokenUri = await erc721.TokenURIQueryAsync(tokenId);

ERC-1155: Multi-Tokens

var erc1155 = web3.Eth.ERC1155.GetContractService(contractAddress);

var balance = await erc1155.BalanceOfQueryAsync(owner, tokenId);
var balances = await erc1155.BalanceOfBatchQueryAsync(owners, tokenIds);
var uri = await erc1155.UriQueryAsync(tokenId);

ERC-165: Interface Detection

var erc165 = web3.Eth.ERC165.GetContractService(contractAddress);

var supportsErc721 = await erc165
    .SupportsInterfaceQueryAsync("0x80ac58cd"); // ERC-721 interface ID

var supportsErc1155 = await erc165
    .SupportsInterfaceQueryAsync("0xd9b67a26"); // ERC-1155 interface ID

// Common interface IDs: ERC-165=0x01ffc9a7, ERC-721=0x80ac58cd, ERC-1155=0xd9b67a26

ERC-1271: Contract Signature Validation

var erc1271 = web3.Eth.ERC1271.GetContractService(contractAddress);

var isValid = await erc1271
    .IsValidSignatureAndValidateReturnQueryAsync(messageHash, signature);

ERC-6492: Pre-Deploy Signature Validation

var isValid = await web3.Eth.ERC6492
    .IsValidSignatureQueryAsync(contractAddress, messageHash, signature);

EIP-3009: Gasless Transfer With Authorization

Low-level:

var eip3009 = web3.Eth.EIP3009.GetContractService(usdcAddress);
var receipt = await eip3009.TransferWithAuthorizationRequestAndWaitForReceiptAsync(
    from, to, value, validAfter, validBefore, nonce, v, r, s);

X402 higher-level (Nethereum.X402):

using Nethereum.X402.Blockchain;
using Nethereum.X402.Models;
using Nethereum.X402.Signers;

// Build authorization + sign with EIP-712
var builder = new TransferWithAuthorisationBuilder();
var authorization = builder.BuildFromPaymentRequirements(requirements, payerAddress);
var signer = new TransferWithAuthorisationSigner();
var signature = await signer.SignWithPrivateKeyAsync(
    authorization, "USDC", "2", chainId, usdcAddress, privateKey);

// Verify + settle
var service = new X402TransferWithAuthorisation3009Service(
    facilitatorKey, rpcEndpoints, tokenAddresses, chainIds, tokenNames, tokenVersions);
var result = await service.VerifyPaymentAsync(paymentPayload, requirements);
var settlement = await service.SettlePaymentAsync(paymentPayload, requirements);

// ReceiveWithAuthorization (receiver pays gas)
var receiveBuilder = new ReceiveWithAuthorisationBuilder();
var receiveService = new X402ReceiveWithAuthorisation3009Service(
    receiverKey, rpcEndpoints, tokenAddresses, chainIds, tokenNames, tokenVersions);

ENS: Name Resolution

var ensService = web3.Eth.GetEnsService();
var address = await ensService.ResolveAddressAsync("vitalik.eth");
var name = await ensService.ReverseResolveAsync(address);

Historical Queries

All query methods accept BlockParameter:

var blockParam = new Nethereum.RPC.Eth.DTOs.BlockParameter(15000000);
var historicalBalance = await erc20.BalanceOfQueryAsync(address, blockParam);

Code-Generated Contract Services (ContractServiceBase)

// Introspect all registered types in a code-generated service
var functionTypes = myContractService.GetAllFunctionTypes();
var eventTypes = myContractService.GetAllEventTypes();
var errorTypes = myContractService.GetAllErrorTypes();

// Get ABI metadata and Keccak signatures
var functionABIs = myContractService.GetAllFunctionABIs();
var eventABIs = myContractService.GetAllEventABIs();
var errorABIs = myContractService.GetAllErrorABIs();
var functionSigs = myContractService.GetAllFunctionSignatures();
var eventSigs = myContractService.GetAllEventsSignatures();
var errorSigs = myContractService.GetAllErrorsSignatures();

Low-Level Storage Access (StorageUtil)

using Nethereum.Contracts.ContractStorage;

// Calculate the storage key for mapping(address => ...) at slot 0
var storageKey = StorageUtil.CalculateMappingAddressStorageKey(ownerAddress, 0);

// Read the raw storage value
var storageValue = await web3.Eth.GetStorageAt
    .SendRequestAsync(contractAddress, storageKey);

Key Rules

• NEVER write raw ABI JSON for standard contracts -- always use typed services
• ALWAYS check Nethereum.Contracts.Standards/ before any contract interaction
• All services accept optional BlockParameter for historical queries
• For batch operations use MultiQueryBatchRpcHandler with CreateMulticallInputOutputRpcBatchItems