erc20 — Стандартный интерфейс для токенов Ethereum

--- name: erc20 description: Query and transfer ERC-20 tokens using Nethereum's built-in typed services (.NET/C#). Use this skill whenever the user asks about ERC-20 tokens, token balances, token transfers, token approvals, allowances, token metadata (name, symbol, decimals), or any fungible token interaction with C# or .NET. user-invocable: true --- # 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` ```bash dotnet add package Nethereum.Web3 ``` ## Get the Service All ERC-20 operations start by getting a typed service for the token's contract address: ```csharp 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: ```csharp 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: ```csharp var balance = await erc20.BalanceOfQueryAsync(myAddress); Console.WriteLine($"Balance: {Web3.Convert.FromWei(balance, decimals)} {symbol}"); ``` ## Transfer Tokens Transfers require a `Web3` instance connected with a funded account. The amount must be in the smallest unit — use `ToWei` with the token's decimals: ```csharp var receipt = await erc20.TransferRequestAndWaitForReceiptAsync( recipientAddress, Web3.Convert.ToWei(100, decimals)); ``` Gas estimation, nonce, and EIP-1559 fees are handled automatically. ## Approve and TransferFrom The approve/transferFrom pattern lets another address (like a DEX or smart contract) spend your tokens. First approve a spending limit, then the spender calls `transferFrom`: ```csharp // Approve the spender var approveReceipt = await erc20.ApproveRequestAndWaitForReceiptAsync( spenderAddress, Web3.Convert.ToWei(1000, decimals)); // Check allowance var allowance = await erc20.AllowanceQueryAsync(myAddress, spenderAddress); ``` Be careful with approvals — approving a large amount gives the spender permission to transfer up to that amount at any time. ## Listen for Transfer Events ERC-20 transfers emit a `Transfer` event. Nethereum ships a built-in `TransferEventDTO` so you don't need to define your own: ```csharp using Nethereum.Contracts.Standards.ERC20.ContractDefinition; var transferEvent = web3.Eth.GetEvent<TransferEventDTO>(contractAddress); var filter = transferEvent.CreateFilterInput( BlockParameter.CreateEarliest(), BlockParameter.CreateLatest()); var transfers = await transferEvent.GetAllChangesAsync(filter); foreach (var t in transfers) { Console.WriteLine($"{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: ```csharp var historicalBalance = await erc20.BalanceOfQueryAsync( myAddress, new BlockParameter(15_000_000)); ``` ## Available Methods | Method | Returns | Description | |--------|---------|-------------| | `NameQueryAsync()` | `string` | Token name | | `SymbolQueryAsync()` | `string` | Token symbol | | `DecimalsQueryAsync()` | `byte` | Decimal places | | `TotalSupplyQueryAsync()` | `BigInteger` | Total supply in wei | | `BalanceOfQueryAsync(address)` | `BigInteger` | Balance in wei | | `AllowanceQueryAsync(owner, spender)` | `BigInteger` | Approved amount | | `TransferRequestAndWaitForReceiptAsync(to, amount)` | `TransactionReceipt` | Transfer tokens | | `ApproveRequestAndWaitForReceiptAsync(spender, amount)` | `TransactionReceipt` | Approve spending | | `TransferFromRequestAndWaitForReceiptAsync(from, to, amount)` | `TransactionReceipt` | Transfer on behalf | For full documentation, see: https://docs.nethereum.com/docs/smart-contracts/erc20