aa-batching-paymasters

Development

Help users batch multiple calls into a single UserOperation and sponsor gas with paymasters using Nethereum Account Abstraction. Use when the user mentions batching transactions, atomic multi-call, approve-then-swap in one tx, gas sponsorship, paymasters, gasless transactions, verifying paymaster, deposit paymaster, or PaymasterConfig in .NET/C# with ERC-4337.

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Batching & Paymasters

Execute multiple contract calls atomically in a single UserOperation, and sponsor gas fees with paymasters so users don't need ETH.

When to Use This

User wants to batch multiple calls (approve + swap, multi-transfer) in one atomic operation
User needs gas sponsorship — a paymaster pays gas instead of the user
User is building gasless UX for their dApp
User mentions BatchExecuteAsync, ToBatchCall, WithPaymaster, or PaymasterConfig

Packages

dotnet add package Nethereum.Web3
dotnet add package Nethereum.AccountAbstraction

Batch Multiple Calls

Typed Batch (Same Contract)

var transfer1 = new TransferFunction { To = "0xRecipient1", Value = Web3.Convert.ToWei(50) };
var transfer2 = new TransferFunction { To = "0xRecipient2", Value = Web3.Convert.ToWei(25) };

var receipt = await handler.BatchExecuteAsync<TransferFunction>(transfer1, transfer2);

Mixed Batch (Different Contracts)

Use ToBatchCall() to convert typed messages:

var approve = new ApproveFunction { Spender = dexAddress, Value = Web3.Convert.ToWei(1000) };
var swap = new SwapFunction { AmountIn = Web3.Convert.ToWei(1000) };

var receipt = await handler.BatchExecuteAsync(
    approve.ToBatchCall(),
    swap.ToBatchCall());

Batch with ETH Value

var depositCall = new DepositFunction().ToBatchCall(Web3.Convert.ToWei(1));

Raw Calldata Batch

var receipt = await handler.BatchExecuteAsync(encodedCallData1, encodedCallData2);

ERC-7579 Batch via SmartAccountService

using Nethereum.AccountAbstraction.BaseAccount.ContractDefinition;

var calls = new[]
{
    new Call { Target = tokenAddress, Value = 0, Data = approveCallData },
    new Call { Target = dexAddress, Value = 0, Data = swapCallData }
};

var receipt = await account.ExecuteBatchAsync(calls);

Paymasters

Simple Paymaster

handler.WithPaymaster(paymasterAddress);
// All subsequent operations use this paymaster for gas

With Static Data

handler.WithPaymaster(paymasterAddress, paymasterData);

Verifying Paymaster (Off-Chain Signature)

var paymaster = web3.GetVerifyingPaymasterAsync(paymasterAddress, paymasterSignerKey);

handler.WithPaymaster(new PaymasterConfig(paymasterAddress, async userOp =>
{
    return await paymaster.GetPaymasterDataAsync(userOp);
}));

Deposit Paymaster (Pre-Funded)

var depositPaymaster = web3.GetDepositPaymasterAsync(paymasterAddress);
handler.WithPaymaster(paymasterAddress);

Dynamic Paymaster Data

handler.WithPaymaster(new PaymasterConfig(paymasterAddress, async userOp =>
{
    // Call external paymaster API at submission time
    var response = await httpClient.PostAsJsonAsync("https://paymaster.example.com/sign",
        new { userOp });
    var result = await response.Content.ReadFromJsonAsync<PaymasterResponse>();
    return result.PaymasterData.HexToByteArray();
}));

Decision Guide

Scenario	Approach
Same-contract multi-call	`BatchExecuteAsync<T>(msg1, msg2)`
Cross-contract atomic ops	`BatchExecuteAsync(msg1.ToBatchCall(), msg2.ToBatchCall())`
Raw calldata	`BatchExecuteAsync(bytes1, bytes2)`
ERC-7579 modular account	`account.ExecuteBatchAsync(Call[])`
Simple gas sponsorship	`handler.WithPaymaster(address)`
Per-operation signature	`PaymasterConfig` with async callback
Pre-funded sponsorship	Deposit paymaster + static address

Common Mistakes

Paymaster not funded — EntryPoint checks paymaster deposit, returns AA31/AA32 errors
Paymaster data expired — verifying paymasters include validity windows; use dynamic data
Wrong batch approach — use ToBatchCall() for cross-contract, generic <T> for same-contract

For full documentation, see: https://docs.nethereum.com/docs/account-abstraction/guide-batching-and-paymasters