aa-batching-paymasters

name	aa-batching-paymasters
description	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.
user-invocable	true

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