I am unable to call a contracts read and write on the same block (as 2 consecutive calls)

Question

I have a project where I am required to read and write to the same block ie.

• Call a view function to check if there is a match on the specific block
• If there is a match from the previous call, call a write function to confirm the match which is only on that specific block

By calling the view function, it ensures I don't have to pay gas fees until a match is actually found. When the match is made, we can then call the paid write function.

In the write function I have a line of code:

require(block.number == blockNumber)

blockNumber is passed in from the output of the view call (the block where the match has been made).

I cannot get this view function match to execute on the same block as the write function even though there is plenty of time to do so (after sending transaction, I check the block number and the current block is still the one expected).

The program making the calls to the contract is a C# program thats uses the Nethereum library.

I have tried the following:

• Hard coded gas to be way above what's expected so I don't have to waste time calling the estimate for the write first
• Given the write function an ungodly price per gas + the same for maxPricePerGas
• Tried executing this on a very very fast machine

Does anyone know how I can solve this problem/is there something I am missing?

Answer 1

One way to ensure read and write in the same block is to execute both actions within the same transaction.

Another option is to use a flashbot service that will ensure both transactions are in the same block by "mining" in the same block.