How to properly use decimal.TryParse and decimal.Parse

Question

I have method in which I try to parse string to decimal number. At first I implemented the method with decimal.Parse and wrapped the body of the method in try catch block. Then I threw exception in catch block when the Parse method had thrown FormatException. I know it's not a good practice to throw exception in a catch block, but I couldn't figure out how to add detailed info about the parsing error. Then I refactored the method to look like this:

public List<ExcelGeneralLedgerRow> ParseGeneralLedger(DataTable worksheet)
        {
            var rows = new List<ExcelGeneralLedgerRow>();
            for (int i = 1; i <= worksheet.Rows.Count - 1; i++)
            {
                var row = worksheet.Rows[i];

                if (!decimal.TryParse(row[3].ToString(), out decimal value))
                {
                    throw new Exception($"detailed info about that exception was thrown on specific row.");
                }

                var syntheticAccountNumber = row[0].ToString();
                var analyticAccountNumber = row[1].ToString();

                if (analyticAccountNumber == String.Empty)
                {
                    analyticAccountNumber = "000";
                }

                var text = row[2].ToString();
                rows.Add(new ExcelGeneralLedgerRow(syntheticAccountNumber, analyticAccountNumber, text, value));
            }

            return rows;
        }

is this a good practice? it seems to me that with this approach I can add more information to the thrown exception. also i can parse more than just one value and add information about which parsing failed. but the code would fast turn to spaghetti code if I implement numerous if statements to throw exception.

Whats your opinion? Is there any other approach?

Thanks.

Answer 1

As was answered by Johnathan Barclay, there is nothing that would limit you from throwing from inside a catch block. There is even a way to catch and rethrow the original exception like this:

try {
   // Do something here that throws exception
} catch(Exception ex) {
   // log the exception
   throw;
   // instead of throw ex; which would reset the information of the original exception
}

You code, while there is nothing wrong with it, would benefit from a more specific Exception. Hence, custom exceptions

class GeneralLedgerParseException : Exception
{

    // Properties with the additional information
    public string //...

    public GeneralLedgerParseException()
    {

    }
}

This way you can even create catch clauses for the specific exceptions and handle them, without catching other generic exceptions.

try {
  //
} 
catch (GeneralLedgerParseException glex) {
  // Any other kind of exception will not be caught here
} 
catch (Exception ex) {
  // All other exceptions will be caught here
}