Question

Module globalVariable

    Public tblScItem As New DataTable
    Public tempArray()
    Public index As Integer
    Public stringArr() As String

End Module

Private Sub txtQty_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtQty.TextChanged

    stringArr = New String() {"", txtItem.Text, Form2.cbGondola.SelectedItem, txtQty.Text, DateTime.Now, Form1.txtLoginId.Text}

    If txtItem.Text <> Nothing And txtQty.Text <> Nothing Then

        index = 0

        tempArray(index) = stringArr

        tblScItem.Rows.Add(tempArray)

        index += 1

    End If

End Sub

My program is a stock take program which works in a way that when the quantity of the item is entered, it will display in a datagrid and at the same time, store in an array. After the entire transaction is done, the entire array is exported to a txt file.

I have declared an array stringArr to store all the details of the an item. Then, i used a tempArray to store each item (which contains all the details in stringArr in the individual index of the tempArray.

Example: 
tempArray(0) = 'details of item 1 obtained from stringArr
tempArray(1) = 'details of item 2 obtained from stringArr
and so on

However, i kept getting ‘object is not set to an instance of an object’ after the quantity is entered.

Anyone know why? I’m in need of help.

Thank you.

Answer 1

You are getting the error message because you haven’t initialised the tempArray variable. It’s just a reference to an array, but it doesn’t have an array to reference.

However, you are trying to put an array in an array, but the DataRowCollection.Add method takes an array, not an array of arrays.

Just use the stringArr variable:

Private Sub txtQty_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtQty.TextChanged

  stringArr = New String() {"", txtItem.Text, Form2.cbGondola.SelectedItem, txtQty.Text, DateTime.Now, Form1.txtLoginId.Text}

  If txtItem.Text <> "" And txtQty.Text <> "" Then

    tblScItem.Rows.Add(stringArr)

  End If

End Sub

Note that the Text property of a control is never Empty, you should check if it is an empty string.

If you want to add the rows to a collection other than the DataTable, you wouldn’t use an array, as it’s not resizable. You would use a List(Of String()):

Public tempList As new List(Of String())

Private Sub txtQty_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtQty.TextChanged

  stringArr = New String() {"", txtItem.Text, Form2.cbGondola.SelectedItem, txtQty.Text, DateTime.Now, Form1.txtLoginId.Text}

  If txtItem.Text <> "" And txtQty.Text <> "" Then

    tempList.Add(stringArr)

    tblScItem.Rows.Add(stringArr)

  End If

End Sub