AX 2012 - Exchange rate edit, calculate, convert currency amount to default amount

Find exchange rate:

ExchangeRateCurrencyPair    pair;

//TCMB : Exchange rate type (ExchangeRateType) tablle Name key field
select firstOnly pair
                    where pair.ExchangeRateType == ExchangeRateType::findByName("TCMB").RecId &&
                        pair.FromCurrencyCode == "USD" &&
                        pair.ToCurrencyCode == Ledger::accountingCurrency(CompanyInfo::current());


this.ExchangeRate = ExchangeRate::findByDate(pair.RecId,systemDateGet()).ExchangeRate;

Edit method for exchange rate entry ( There're a lot of samples at default forms like SalesTable ) :

public edit CurrencyExchangeRate editExchRate(boolean set, CurrencyExchangeRate _exchRate)
{
    ExchangeRateHelper exchangeRateHelper = ExchangeRateHelper::newCurrency(Ledger::primaryLedger(CompanyInfo::findDataArea(curext()).RecId), this.Currency);

    if (set)
    {
        this.ExchangeRate = exchangeRateHelper.prepareExchangeRateForStorage(_exchRate);
    }
    else
    {
        _exchRate = exchangeRateHelper.displayStoredExchangeRate(this.ExchangeRate);
    }

    return _exchRate;
}

Calculate default currency amount from exchange rate:
ExchangeRateHelper exchangeRateHelper = ExchangeRateHelper::newCurrency(Ledger::primaryLedger(CompanyInfo::findDataArea(curext()).RecId), Ledger::accountingCurrency(CompanyInfo::current()));
 CurrencyExchangeHelper  cur = CurrencyExchangeHelper::construct();
   
cur.parmLedgerRecId(Ledger::primaryLedger(CompanyInfo::current()));
cur.parmExchangeDate(today());
//If you want to find daily currency rate from system, delete next two lines 
 cur.parmExchangeRate1(exchangeRateHelper.prepareExchangeRateForStorage(1));
cur.parmExchangeRate2(this.ExchangeRate);
    this.BudgetAmountMST = cur.calculateTransactionToAccounting(this.Currency,this.BudgetAmount,true);

or short type of upper:

info(strFmt("%1", Currency::curAmount(100,"usd",today(),UnknownNoYes::Yes,500,100)));

    info(strFmt("%1", Currency::curAmount2CurAmount(100,"usd","try",today())));