Refactoring help with Ifs

Question

I've been working on this code for awhile and for some reason all the if's are driving me crazy along with a bunch of repeated code. Is there a nicer more cleaner way to do this?

public Program(string[] args)
    {
        try
        {
            WriteToLogFile("Starting ImportTask");
            if (args.Length == 0)
            {
                Import(DateTime.Now,DateTime.Now);
                MarkRecordsAsDeleted();
            }
            else if (args.Length == 1)
            {
                DateTime dateToImport;
                bool isValidDate = DateTime.TryParse(args[0], out dateToImport);
                if (isValidDate)
                {
                    Import(dateToImport,dateToImport);
                    MarkRecordsAsDeleted();
                }
                else
                    WriteToLogFile(String.Format("The Import date specified was invalid. - {0}", args[0]));
            }
            else if (args.Length == 2)
            {
                DateTime importStartDate;
                bool isValidStartDate = DateTime.TryParse(args[0], out importStartDate);
                DateTime importEndDate;
                bool isValidEndDate = DateTime.TryParse(args[0], out importEndDate);
                if (isValidStartDate && isValidEndDate)
                {
                    if (importStartDate > importEndDate)
                    {
                        WriteToLogFile(String.Format("Invalid date range provided. Start date = {0} End date {1}",importStartDate,importEndDate));
                        return;
                    }
                    Import(importStartDate, importEndDate);
                    MarkRecordsAsDeleted();
                }
                else
                    WriteToLogFile(String.Format("The Import date specified was invalid. - {0}", args[0]));
            }
            else
            {
                WriteToLogFile("Invalid Command Line Parameters Specified");
            }

        }
        catch (Exception ex)
        {
            WriteToLogFile("Error in Import Process = " + ex.StackTrace);
        }
    }

Answer 1

What you've got here is a two-argument function that is expecting strings that can parse to dates. If the second argument is missing, you use the first argument; if the first is missing, you use DateTime.Now.

So, write a two-argument function that takes two dates. Call it. Something along the lines of:

switch(args.length) {
    case 0: myFunc(DateTime.Now, DateTime.Now); break;
    case 1: myFunc(toDate(args[0]), toDate(args[0])); break;
    case 2: myFunc(toDate(args[0]), toDate(args[1])); break;
}

By the way, it appears that you are not referring to args[1] in your function; that's probably a bug.

Answer 2

Here's a first pass:

public Program(string[] args)
{
    try
    {
        WriteToLogFile("Starting ImportTask");
        DateTime startTime;
        DateTime endTime;
        GetDateRange(args, out startTime, out endTime);

        Import(startTime, endTime);
        MarkRecordsAsDeleted();
    }
    catch (Exception ex)
    {
        WriteToLogFile("Error in Import Process = " + ex);
        throw;
    }
}

    private static void GetDateRange(string[] args, out DateTime startTime, out DateTime endTime)
    {
        switch (args.Length)
        {
            case 0:
                startTime = DateTime.Now;
                endTime = DateTime.Now;
                break;
            case 1:
                {
                    DateTime dateToImport;
                    var isValidDate = DateTime.TryParse(args[0], out dateToImport);
                    if (!isValidDate)
                    {
                        throw new Exception(
                            String.Format(
                                "The Import date specified was invalid. - {0}",
                                args[0]));
                    }

                    startTime = dateToImport;
                    endTime = dateToImport;
                }
                break;
            case 2:
                {
                    DateTime importStartDate;
                    bool isValidStartDate = DateTime.TryParse(args[0], out importStartDate);
                    DateTime importEndDate;
                    bool isValidEndDate = DateTime.TryParse(args[1], out importEndDate);
                    if (!isValidStartDate || !isValidEndDate)
                    {
                        throw new Exception(
                            String.Format(
                                "The Import dates specified was invalid. - {0}, {1}",
                                args[0], args[1]));
                    }

                    if (importStartDate > importEndDate)
                    {
                        throw new Exception(
                            String.Format(
                                "Invalid date range provided. Start date = {0} End date {1}",
                                importStartDate, importEndDate));
                    }

                    startTime = importStartDate;
                    endTime = importEndDate;
                }
                break;
            default:
                throw new Exception("Invalid Command Line Parameters Specified");
        }
    }