Can anyone Resolve this NullReferenceException?

Question

I'm pasting the whole code, for the ease of you, in this the bold line was giving continues error:

Option Explicit On
Option Compare Text

Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Windows.Forms
Imports Microsoft.Office.Interop.Excel


Public Class TestForm

    Private Sub TestForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x() As Object = {2.648305, 4.934211, 7.04005, 9.014423, 11.09467, 13.0814, 15.06889, 17.08428}
        Dim y() As Object = {15, 30, 45, 60, 75, 90, 105, 120}
        Dim z(y.Length - 1) As Object
        Dim i, j, k As Integer
        Dim xstr, ystr, zstr As String
        Dim exApp As Microsoft.Office.Interop.Excel.WorksheetFunction
        Try
            For i = 0 To x.Length
                For j = 0 To y.Length
                    For k = 0 To z.Length
                        z(k) = exApp.Slope(y(j), x(i))
                    Next
                Next
            Next
            For i = 0 To x.Length
                xstr += x(i).ToString()
            Next
            For j = 0 To y.Length
                ystr += y(j).ToString()
            Next
            For k = 0 To z.Length
                zstr += z(k).ToString()
            Next
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
        xLabel.Text = "X=" + xstr.ToString()
        yLabel.Text = "Y=" + ystr.ToString()
        zLabel.Text = "Z=" + zstr.ToString()
    End Sub
End Class

The Bold Line always gives the same error:
System.NullReferenceException was caught
  Message="Object reference not set to an instance of an object."
  Source="AdsorptionSimulator"
  StackTrace:
       at ChemChart.TestForm.Button1_Click(Object sender, EventArgs e) in C:\ChemChart\ChemChart\Forms\TestForm.vb:line 39
  InnerException:

Please Can Anyone Help me, I need the Code urgently.

Thanx in advance,

- Rajeev

Answer 1

Hi Rajeev,

Use 'Length - 1' as the upperlimit.
The follownig may work.

For i = 0 To x.Length -1
                For j = 0 To y.Length -1
                    For k = 0 To z.Length -1
                        z(k) = exApp.Slope(y(j), x(i))
                    Next
                Next
            Next

hope this helps.

Regards,
Kalyan