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POCannot access the second item in the list
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  1. POCannot access the second item in the list
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    copied!<p>I am having trouble accessing the second item in the list and I cannot see why any help would be appreciated.</p> <pre><code>class Datapoints { List&lt;Datapoint&gt; datapoints; //Creates a list of datapoints from Datapoint private string fileName; public string Filename { get { return fileName; } } public Datapoint GetDatapoint(int i) //Creates an instance of a Datapoint called GetDatapoint { if (i &lt; datapoints.Count) return datapoints[i]; else return null; } public Datapoints(string fName) //Method that creates a new list of datapoints with the objects of Datapoint within it { this.fileName = fName; datapoints = new List&lt;Datapoint&gt;(); TextReader tr = new StreamReader(fileName); string input; while ((input = tr.ReadLine()) != null) { string[] bits = input.Split(','); Datapoint a = new Datapoint(bits[0], bits[1], bits[2]); datapoints.Add(a); } tr.Close(); } </code></pre> <p>Here is the form, what I am trying to make happen is to have the boxes show the three numbers in the file when pressing the next button.</p> <pre><code>private void InitTextBoxes() { if (myDatapoints.Count &gt; 0) { Datapoint a = myDatapoints.getItem(0); textBoxLatitude.Text = a.Latitude; textBoxLongtitude.Text = a.Longtitude; textBoxElevation.Text = a.Elevation; buttonNext.Enabled = true; buttonPrevious.Enabled = true; } count = 0; textBoxLatitude.Enabled = false; textBoxLongtitude.Enabled = false; textBoxElevation.Enabled = false; buttonDone.Visible = false; buttonDone.Enabled = false; addingData = false; saved = true; openToolStripMenuItem.Enabled = false; } private void openToolStripMenuItem1_Click(object sender, EventArgs e) { OpenFileDialog ofd = new OpenFileDialog(); ofd.Filter = "Csv Files (*.csv)|*.csv|Text files (*.txt)|*.txt|All files (*.*)|*.*"; if (ofd.ShowDialog(this).Equals(DialogResult.OK)) { myDatapoints = new Datapoints(ofd.FileName); this.Text = "Data Entry - " + ofd.SafeFileName; InitTextBoxes(); if (myDatapoints.Count &gt; 0) { buttonNext.Enabled = true; buttonPrevious.Enabled = true; closeToolStripMenuItem.Enabled = true; saveAsToolStripMenuItem.Enabled = true; } } } private void buttonNext_Click(object sender, EventArgs e) { count++; if (count == myDatapoints.Count) count = 0; Datapoint a = myDatapoints.getItem(count); textBoxLatitude.Text = a.Latitude; textBoxLongtitude.Text = a.Longtitude; textBoxElevation.Text = a.Elevation; textBoxTest.Text = Convert.ToString(myDatapoints.Count); } private void buttonPrevious_Click(object sender, EventArgs e) { } </code></pre> <p>Also, when I initiate the boxes, I cannot change the datapoints.GetItem to anything but (0) as if i do there is an error in the following line I believe this is the heart of the problem but I cannot see why. The error is </p> <blockquote> <p>Object reference not set to an instance of an object. </p> </blockquote> <p>Within the file I am using to test there are 9 numbers (1,2,3,4,5,6,7,8,9) so it ought to take the middle three when I select 1, bit it doesn't!</p> <pre><code> internal Datapoint getItem(int p) { if (p &lt; datapoints.Count) { return datapoints[p]; } else return null; } </code></pre>
 

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