public async Task <OperationResult> Deposit(int userId, decimal amount, string currency)
{
var wallet = await walletManager.GetUserWallet(userId, currency);
if (wallet == null)
{
await walletManager.CreateUserWallet(userId, currency, amount);
}
else
{
wallet.Amount += amount;
await walletManager.UpdateUserWallet(wallet);
}
return(new OperationResult(true, String.Empty));
}