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Send Transactions Using the Transaction Manager

The TransactionManager handles gas estimation, nonce management, and EIP-1559 fees automatically — you just provide the recipient, data, and optionally a value. This guide covers sending transactions with data (calling a smart contract, storing a message on-chain). For simple ETH transfers, see Transfer Ether. Data is encoded as hex using .ToHexUTF8() and similar extension methods (see Hex Encoding).

dotnet add package Nethereum.Web3

Send a Transaction with Data​

using Nethereum.Web3;
using Nethereum.Web3.Accounts;
using Nethereum.Hex.HexConvertors.Extensions;
using Nethereum.Hex.HexTypes;
using Nethereum.RPC.Eth.DTOs;

var privateKey = "0x7580e7fb49df1c861f0050fae31c2224c6aba908e116b8da44ee8cd927b990b0";
var chainId = 444444444500; // Nethereum testchain
var account = new Account(privateKey, chainId);
Console.WriteLine("Our account: " + account.Address);

var web3 = new Web3(account, "http://testchain.nethereum.com:8545");

var txnInput = new TransactionInput();
txnInput.From = account.Address;
txnInput.To = "0x12890d2cce102216644c59daE5baed380d84830c";
txnInput.Data = "Hello".ToHexUTF8();
txnInput.Gas = new HexBigInteger(900000);

var receipt = await web3.Eth.TransactionManager
    .SendTransactionAndWaitForReceiptAsync(txnInput);
Console.WriteLine("Has errors: " + receipt.HasErrors().Value);

HasErrors() returns true if the receipt status indicates a revert.

Estimate Gas Before Sending​

var txnInput = new TransactionInput()
{
    From = account.Address,
    To = "0x1bb31d596c34bd81e1f0be1edf3840a7b43dd9cd",
    Data = "0x7b2274657374..."
};

var gasEstimate = await web3.Eth.TransactionManager.EstimateGasAsync(txnInput);
Console.WriteLine("Estimated gas: " + gasEstimate.Value);
txnInput.Gas = gasEstimate;

var txnHash = await web3.Eth.TransactionManager.SendTransactionAsync(txnInput);
Console.WriteLine("Transaction hash: " + txnHash);

Send Without Waiting for Receipt​

Use SendTransactionAsync to get the transaction hash immediately without waiting for it to be mined:

var txnHash = await web3.Eth.TransactionManager.SendTransactionAsync(txnInput);

More Control: Explicit Fee Parameters​

By default, Nethereum sends EIP-1559 transactions and calculates fees automatically. The sections below are optional — use them only when you need to override the automatic behavior.

EIP-1559 Fee Parameters​

To set fees explicitly, use MaxFeePerGas and MaxPriorityFeePerGas on the TransactionInput (see Fee Estimation for strategies):

using Nethereum.Util;

var txnInput = new TransactionInput()
{
    From = account.Address,
    To = "0x12890d2cce102216644c59daE5baed380d84830c",
    Data = "Hello".ToHexUTF8(),
    Gas = new HexBigInteger(900000),
    MaxFeePerGas = new HexBigInteger(Web3.Convert.ToWei(50, UnitConversion.EthUnit.Gwei)),
    MaxPriorityFeePerGas = new HexBigInteger(Web3.Convert.ToWei(2, UnitConversion.EthUnit.Gwei))
};

var receipt = await web3.Eth.TransactionManager
    .SendTransactionAndWaitForReceiptAsync(txnInput);

Setting GasPrice instead triggers a legacy transaction automatically.

Legacy Transactions​

To use legacy transactions by default:

web3.TransactionManager.UseLegacyAsDefault = true;

EIP-7702: Inline Authorization​

You can attach an EIP-7702 authorization directly to a transaction, delegating an EOA and executing a contract call in one step. The transaction manager signs unsigned authorizations automatically and calculates the extra gas overhead:

var executeFunction = new ExecuteFunction
{
    Calls = batchCalls,
    Gas = 1000000,
    AuthorisationList = new List<Authorisation>
    {
        new Authorisation { Address = "0xDelegateContractAddress" }
    }
};

var receipt = await contractService.ExecuteRequestAndWaitForReceiptAsync(executeFunction);

For dedicated delegation workflows (self-delegation, sponsored delegation, batch delegation), see the EIP-7702 guide.

Next Steps​