Untitled

 List<string> currencies = new List<string>()
 {
     "USD",
     "EUR",
     "GBP",
     "RON",
 };
 comboBox1.Items.Clear();
 comboBox2.Items.Clear();
 comboBox1.Items.AddRange(currencies.ToArray());
 comboBox2.Items.AddRange(currencies.ToArray());
 comboBox1.SelectedItem = "USD";
 comboBox2.SelectedItem = "EUR";


 string fromCurrency =comboBox1.SelectedItem.ToString();
 string toCurrency =comboBox2.SelectedItem.ToString();
 double amount;

 if(!double.TryParse(textBox1.Text, out amount))
 {
     MessageBox.Show("Te rog sa introduci o suma valida");
     return;
 }
 double convertedAmount = 0;
   if(fromCurrency == "USD" && toCurrency == "EUR")
 {
     convertedAmount = 0.85 * amount;
 }
 else if (fromCurrency == "EUR" && toCurrency == "USD")
 {
     convertedAmount = 1.18 * amount;
 }
 else if (fromCurrency == "GBP" && toCurrency == "RON")
 {
     convertedAmount = 5.5 * amount;
 }
 else if (fromCurrency == "RON" && toCurrency == "GBP")
 {
     convertedAmount = 0.18 * amount;
 }
 else if (fromCurrency == "USD" && toCurrency == "RON")
 {
     convertedAmount = 4.10 * amount;
 }
 else if(fromCurrency == "RON" && toCurrency == "USD")
 {
     convertedAmount = 0.24 * amount;
 }