Reading text files from local folder

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Hi I am trying to read text files with the help of stream reader, but i got this error "An exception of type 'System.NullReferenceException' occurred in DevotionText.DLL but was not handled in user code" when i try running it in the emulator

The code below

C#

// xaml.cs
public partial class MainPage : PhoneApplicationPage
    {
        List<string> devotions = new List<string>();
        
        // Constructor
        public MainPage()
        {
            InitializeComponent();

            AddDevotions(); 

            // Sample code to localize the ApplicationBar
            //BuildLocalizedApplicationBar();
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            DateTime dt = DateTime.Now;
            int month = dt.Month;
            int year = dt.Year;
            int index;

            if (DateTime.IsLeapYear(year) || (month <= 2))
            {
                index = dt.DayOfYear - 1; // list is indexed from 0
            }
            else
            {
                index = dt.DayOfYear; // add a day
            }

            textblock.Text = devotions[index].ToString(); // or some other property
        }

        private void AddDevotions()
        {
            for (int i = 1; i <= 366; i++)
            {
                string filePath = "Devotions/Devotion1" + i.ToString() + ".txt";
                
                devotions.Add(d);
            }
        }

        public string ReadTextFile(string textFilePath)
        {
            string text = null;

            using (StreamReader r = new StreamReader(textFilePath))
            {
                text = r.ReadToEnd();
            }

            return text;
        }

        public string d { get; set; }

Kindly help

Posted 2-Feb-15 4:45am

Member 10627743

Updated 2-Feb-15 5:27am

Kenneth Haugland

v2

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Comments

ZurdoDev 2-Feb-15 10:58am

Which line of code causes the error?

Member 10627743 2-Feb-15 11:10am

The error occur on the following line " textblock.Text = devotions[index].ToString(); // or some other property"

ZurdoDev 2-Feb-15 11:21am

That means devotions[index] is null.

Herman<T>.Instance 2-Feb-15 11:47am

exactly or textblock is null. I don't see any declaration for textblock.
Futhermore strange code. It starts in the constructor with adding devitions before the file is read!

Member 10627743 2-Feb-15 12:35pm

I have corrected the code but am still getting the same error, see the code below

public partial class MainPage : PhoneApplicationPage
{
List<string> devotions = new List<string>();

// Constructor
public MainPage()
{
InitializeComponent();

AddDevotions();
int index = DateTime.Now.DayOfYear;
textblock.Text = devotions[index];

// Sample code to localize the ApplicationBar
//BuildLocalizedApplicationBar();
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
DateTime dt = DateTime.Now;
int month = dt.Month;
int year = dt.Year;
int index;

if (DateTime.IsLeapYear(year) || (month <= 2))
{
index = dt.DayOfYear - 1; // list is indexed from 0
}
else
{
index = dt.DayOfYear; // add a day
}

textblock.Text = devotions[index].ToString(); // or some other property
}

private void AddDevotions()
{
for (int i = 1; i <= 366; i++)
{
string filePath = "Devotions/Devotion1" + i.ToString() + ".txt";

devotions.Add(d);
}
}

public string ReadTextFile(string textFilePath)
{
string text = null;

using (StreamReader r = new StreamReader(textFilePath))
{
text = r.ReadToEnd();
}

return text;
}

public string d { get; set; }

BillWoodruff 2-Feb-15 11:57am

So, having set a break-point on that line, run the program and when it stops at the break-point inspect the value of every reference on that line, and then figure out why the null value is null.

1 solution

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Richard Deeming · Answer 1 · 2015-02-02T06:05:00

C#

private void AddDevotions()
{
    for (int i = 1; i <= 366; i++)
    {
        string filePath = "Devotions/Devotion1" + i.ToString() + ".txt";

        devotions.Add(d);
    }
}

Since your code never sets the auto property d to anything, every item in your devotions list will be null. When you try to call .ToString() on a null reference, you will get a NullReferenceException.

I suspect that you meant to read the file from filePath into the list? If so, try the following:

C#

private void AddDevotions()
{
    for (int i = 1; i <= 366; i++)
    {
        string filePath = Path.GetFullPath("Devotions/Devotion1" + i.ToString() + ".txt");
        
        if (File.Exists(filePath))
        {
            devotions.Add(File.ReadAllText(filePath));
        }
        else
        {
            devotions.Add(string.Format("Devotions file '{0}' was not found.", i));
        }
    }
}