string chainIDString = "CHAIN-ID-HERE";
// First Convert the chain id string into a byte[]. The API has a build in converter.
byte[] chainIDBytes = Strings.DecodeHexIntoBytes(chainIdString);
// Now we can get all the entries in the chain, a List of EntryData will be returned.
var entries = Chain.GetAllChainEntries(chainIDBytes);
//Each index in entries contains the Entry hash and timestamp. To get it's content, use:
index = 0; // Index of entry you want to get
byte[] content = Entry.GetEntryData(entries[index].Entryhash);

int cost = Entry.EntryCost(entry);

cost += 10;

/// The call to make a new entry is Entry.NewEntry(byte[] content, byte[][] extIds, byte[] chainId)
/// content: The data you wish the entry to store
/// extIds: Used to generate a UNIQUE chainID. These will take up space in the Entry, and make these unique
///         for each new chain you create.
/// chainId: Leave null for the first entry, as it is computed by the extIds

byte[] content = Encoding.UTF8.GetBytes("This is my entry content");
// One idea is to use a hash of your content, or use a random number. You can use any number of extIds,
// here I use 2.
byte[][] extIDs = new[] {
            Encoding.UTF8.GetBytes("random-string-of-things"),
            Encoding.UTF8.GetBytes("this-will-hopefully-be-unique")
            }
var firstEntry = Entry.NewEntry(content, extIds, null);
// Now we can make our chain to commit.
var chain = Chain.NewChain(firstEntry);

// Factom is not free, you need a entry credit wallet. Put the name of your wallet here:
string walletName = "What you named your wallet";
byte[] chainID = Chain.CommitChain(chain, walletName);

Thread.Sleep(10000); // Must wait 10 seconds

Chain.RevealChain(chain); // Must reveal the entry
// If all went well your entry is now on Factom!
// DO NOT LOSE 'chainID'. This is how you find your chain after it is made, so make it a form of output
// and hang onto it

// We have to make another Entry like before, but now we do not need the extIds.
byte[] content = Encoding.UTF8.GetBytes("Some more content to add!");
// Convert the chainID string into byte[] if it's not already. I use a function I made, you can too.
// You can also use the chainID returned from the commit earlier.
byte[] chainId = Strings.DecodeHexIntoBytes("HEX-STRING-HERE"); //Should be in hex, case does not matter
var entry = Entry.NewEntry(content, null, chainId);

// Factom is not free, you need a entry credit wallet. Put the name of your wallet here:
string walletName = "What you named your wallet";
Entry.CommitEntry(entry, factomWalletName);

Thread.Sleep(10000); // Must wait 10 seconds

Entry.RevealEntry(factomEntry);
// Your entry is now on the chain if there are no exceptions.