System.NullReferenceException error in Program

Question

In my program, I'm getting the error:

An unhandled exception of type 'System.NullReferenceException' occurred in POS    System.exe

Additional information: Object reference not set to an instance of an object.

This happens when I try to add something to TransactionList as shown below. TransactionList is a list of class instances, declared like this:

public static List<Transaction> TransactionList { get; set; }

And this is the Transaction class:

class Transaction
{
    public double TotalEarned { get; set; }
    public double TotalHST { get; set; }
    public double TotalCost { get; set; }
    public string Category { get; set; }
    public int DaysSince2013 { get; set; }
}

Any clue whats wrong here? I can't seem to find why this error is being thrown... Thanks!

for (int i = 0; i < (lines / 5); i++)
        {
            TransactionList.Add(new Transaction //Error happens on this line
            {
                TotalEarned = Convert.ToDouble(stringArray[(i * 5)]),
                TotalCost = Convert.ToDouble(stringArray[(i * 5) + 1]),
                TotalHST = Convert.ToDouble(stringArray[(i * 5) + 2]),
                Category = stringArray[(i * 5) + 3],
                DaysSince2013 = Convert.ToInt32(stringArray[(i * 5) + 4])
            });
        }

Use the debugger: either TransactionList or stringArray are most likely null. — Tim S.
– Tim S., Commented Oct 24, 2013 at 18:20

gleng · Accepted Answer · 2013-10-24 18:22:29Z

6

Just initialize it before your for loop ?

if (TransactionList == null)
   TransactionList = new List<Transaction>();

for (int i = 0; i < (lines / 5); i++)
        {
            TransactionList.Add(new Transaction //Error happens on this line
            {
                TotalEarned = Convert.ToDouble(stringArray[(i * 5)]),
                TotalCost = Convert.ToDouble(stringArray[(i * 5) + 1]),
                TotalHST = Convert.ToDouble(stringArray[(i * 5) + 2]),
                Category = stringArray[(i * 5) + 3],
                DaysSince2013 = Convert.ToInt32(stringArray[(i * 5) + 4])
            });
        }

Or if you don't like that, since you've declared it as static, you could do:

public static List<Transaction> TransactionList = new List<TransactionList>();

answered Oct 24, 2013 at 18:22

gleng

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Comments

Saranya · Accepted Answer · 2013-10-24 18:24:21Z

0

You have to initilize the list before using it. When you get Object reference not set to an instnce error, it means the object physically doesnot exist

answered Oct 24, 2013 at 18:24

Saranya

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Comments

PauloHDSousa · Accepted Answer · 2013-10-25 13:31:56Z

-2

Proprably TransactionList and or stringArray are both null.

try to do this

public static List TransactionList { get; set; }

if(TransactionList  == null)
   TransactionList  = new List<Transaction>();

edited Oct 25, 2013 at 13:31

answered Oct 24, 2013 at 18:26

PauloHDSousa

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3 Comments

LarsTech Over a year ago

That doesn't compile.

CSharpie Over a year ago

You cant initialize auto-properties like this.

Brian Over a year ago

If you re-work your answer and format your code correctly, I will remove the down vote.

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