When my form for creating a group of students loads up, I receive a NullReferenceException for seemingly no reason. This is the code that handles the form loading:
Private Sub AddGroupForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
For i As Integer = 0 To Form1.lstStudents.Items.Count - 1
lstStudentList.Items.Add(Form1.lstStudents.Items.Item(i))
Next
tempStudentList.AddRange(Form1.mainStudentList)
btnAllOut.Enabled = False
btnOneOut.Enabled = False
End Sub
The mainStudentList referred to is a list that is populated upon loading by using MySQL:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Try
Dim conn As New MySqlConnection("server=localhost;user=root;database=new_project;port=3306;password=********;")
conn.Open()
Dim command As New MySqlCommand("SELECT * FROM students WHERE deleted=0 ORDER BY lastName;", conn)
Dim dataSet As New DataSet()
Dim dataAdapter As New MySqlDataAdapter()
dataAdapter.SelectCommand = command
dataAdapter.Fill(dataSet, "students")
Dim dataTable As DataTable = dataSet.Tables("students")
For Each row As DataRow In dataTable.Rows
Dim newStudent As New Student
newStudent.intIDNum = row.Item("passCode")
newStudent.strFirstName = row.Item("firstName")
newStudent.strLastName = row.Item("lastName")
newStudent.chrGender = row.Item("gender")
newStudent.dateDOB = row.Item("dateOfBirth")
newStudent.intAge = CInt(Today.Year - newStudent.dateDOB.Year)
newStudent.intYearGroup = row.Item("yearGroup")
newStudent.intSkillLevel = SByte.Parse(row.Item("skillLevel"))
mainStudentList.Add(newStudent)
lstStudents.Items.Add(newStudent.nameConcat(newStudent.strFirstName, newStudent.strLastName))
Next
conn.Close()
Catch ex As Exception
MsgBox("Error: " & ex.ToString())
End Try
End Sub
The specific exception occurs when the tempStudentList attempts to load the values in the mainStudentList. Specifically, it states that "Object reference not set to instance of an Object".
