Get ERC20 balance of token holder as of block number with C# Nethereum and Infura

Question

When this code runs, it throws an error "RpcResponseException: header not found", and I don't understand why or how to fix it. Any advice?

Notes: I am using Nethereum in C#.net and using Infura API

[Function("balanceOf", "uint256")]
public class BalanceOfFunction : FunctionMessage
{
    [Parameter("address", "_owner", 1)]
    public string Owner { get; set; }
}



public void QueryingForBalanceAtBlockNumberWorksAsExpected()
{
    HexBigInteger blockNumber = new HexBigInteger("10933333");
    var web3 = new Nethereum.Web3.Web3("https://mainnet.infura.io/v3/" + _InfuraAPIKey);

    string contractAddress = "0x514910771af9ca656af840dff83e8264ecf986ca"; //chainlink

    string accountAddress = "0x56d065849ef9c59c1bc5ba54b9f96caba5c88812";
    
    var balanceOfFunctionMessage = new BalanceOfFunction()
    {
        Owner = accountAddress,
    };

    var balanceHandler = web3.Eth.GetContractQueryHandler<BalanceOfFunction>();

    //THIS WILL THROW AN ERROR "RpcResponseException: header not found":
    var balanceInBaseUnits = balanceHandler.QueryAsync<BigInteger>(contractAddress, balanceOfFunctionMessage, new Nethereum.RPC.Eth.DTOs.BlockParameter(blockNumber)).Result;
}

Answer 1

I have been told that:

this will be due when trying to query a very old block and the public node is not an archiving one. (Maintaining all the previous States)

https://infura.io/pricing has an "add-on" for "Archiving Data" for $250/month which appears to be the answer.

also relevant: https://infura.io/docs/ethereum/add-ons/archiveData