Question

Alright, I have a class “EIR” which is a List based from its base class “ExpenseReport” as such:

    using System;
using System.Collections.Generic;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.IO;
using System.Linq;
using System.Text;

namespace Payroll
{
    [Serializable]
    public class EIR : List<ExpenseItem>
    {   

    public void WriteToFile(string filename)
        {
            try
            {
                BinaryFormatter formatter = new BinaryFormatter();
                FileStream stream = new FileStream("D:\\myExpensesUpdated.bin", FileMode.Create, FileAccess.Write, FileShare.None);
                formatter.Serialize(stream, filename);
                stream.Close();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Unable to serialize Expenses: {0}", ex.Message);
            }
        }

        public static EIR ReadFromFile(string filename)
    {
        EIR iRost = new EIR();
        try
        {
            BinaryFormatter formatter = new BinaryFormatter();
            FileStream stream = new FileStream("D:\\myExpensesUpdated.bin", FileMode.Open, FileAccess.Read, FileShare.Read);
            iRost = (EIR)formatter.Deserialize(stream);

        }
        catch (Exception ex)
        {
            Console.WriteLine("Unable to deserialize Expenses: {0}", ex.Message);
        }

        return iRost;            
    }            
        }
    }
}

This ReadFromFile part is where I’m having a problem:

In the main program, this portion tries to call ReadFromFile and display newly updated items but I get the error “Unable to cast object of type ‘System.String’ to type ‘Payroll.EIR'”.

try
        {
            EIR expensesUpdated = EIR.ReadFromFile("D:\\myExpensesUpdated.bin");
            foreach (var e in expensesUpdated) Console.WriteLine("Updated: {0}", e.ToString());
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }

How do I get the iRost to cast to the Payroll.EIR which is a class? Is there some way to convert a serialized string to a class?

Answer 1

Your problem is already in WriteToFile function where you are actually serializing the filename instead of the class. I didn’t try it but this should work:

public void WriteToFile(string filename)
{
    try
    {
        BinaryFormatter formatter = new BinaryFormatter();
        FileStream stream = new FileStream(filename, FileMode.Create, FileAccess.Write, FileShare.None); // filename parameter instead of fixed path
        formatter.Serialize(stream, this); // class instance instead of filename parameter
        stream.Close();
    }
    catch (Exception ex)
    {
        Console.WriteLine("Unable to serialize Expenses: {0}", ex.Message);
    }
}

public static EIR ReadFromFile(string filename)
{
    EIR iRost = new EIR();
    try
    {
        BinaryFormatter formatter = new BinaryFormatter();
        FileStream stream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read); // filename parameter instead of fixed path
        iRost = (EIR)formatter.Deserialize(stream);
    }
    catch (Exception ex)
    {
        Console.WriteLine("Unable to deserialize Expenses: {0}", ex.Message);
    }

    return iRost;            
}            

Are you sure it’s a good idea to silently catch all exceptions and just write a message to console?