Object reference not set to instance of an object in VB.NET

Question

Why am I getting the error "Object reference not set to instance of an object" with my code?

Public Class Form2
  Dim i As Integer = 0

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMainMenu.Click
        Me.Close()
    End Sub

  Private Sub btnEnterPatient_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnterPatient.Click

        Names(i) = txtPatientName.Text
        i = i + 1
  End Sub
End Class

Names() is a global variable

Thanks

Updated:

Module Module1
    Public Names() As String
    Public Heights() As Integer
    Public Weights() As Integer
End Module


Public Class Form2

    Dim i As Integer = 0

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMainMenu.Click
        Me.Close()
    End Sub

    Private Sub btnEnterPatient_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnterPatient.Click


        ReDim Preserve Names(0 To i)
        Names(i) = txtPatientName.Text

        ReDim Preserve Heights(0 To i)
        Heights(i) = txtPatientHeight.Text

        ReDim Preserve Weights(0 To i)
        Weights(i) = txtPatientWeight.Text

        i = i + 1

    End Sub
End Class

Which line you are getting error? What is Names? Is it array? Where is code for Names? — DevelopmentIsMyPassion
– DevelopmentIsMyPassion, Commented Jan 24, 2014 at 9:08
The error is pointing to: Names(i) = txtPatientName.Text, Names is an array and it is declared as a global variable across all forms in the module — Marcel
– Marcel, Commented Jan 24, 2014 at 9:10
I am sure you are not able to access this variable and hence getting error? can you show how Names is declared — DevelopmentIsMyPassion
– DevelopmentIsMyPassion, Commented Jan 24, 2014 at 9:11

score 1 · Accepted Answer · 2014-01-24 11:11:36Z

1

If you insist on using a module, you should redim preserve your array.

Public Module Module1
    Public i As Integer = 0
    Public Names() As String
    Public Heights() As Integer
    Public Weights() As Integer
End Module

Public Class Form1
    Dim i As Integer = 0

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.Close()
    End Sub

    Private Sub btnEnterPatient_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click


        ReDim Preserve Names(0 To i)
        Names(i) = txtpatientName.Text

        ReDim Preserve Heights(0 To i)
        Heights(i) = txtpatientheight.Text

        ReDim Preserve Weights(0 To i)
        Weights(i) = txtpatientweight.Text

        i = i + 1

    End Sub


    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        For Each j In Names
            MsgBox(j.ToString)
        Next

    End Sub
End Class

edited Jan 24, 2014 at 11:11

answered Jan 24, 2014 at 10:18

user2990854

Sign up to request clarification or add additional context in comments.

14 Comments

Marcel Over a year ago

thankyou the code for button 2 worked for me, however 'i' will only increment once on the first click and after entering another name, it does not increment

user2990854 Over a year ago

well I is dimensioned in form1. add I into your module. ` Public i As Integer = 0`

user2990854 Over a year ago

honestly from the same form (form1) it should have worked the same but to make it compatible across forms you would need to anyway.

Marcel Over a year ago

I added it into my module however it still does not increase after it reaches 1

user2990854 Over a year ago

add MsgBox(i.ToString) to button2 after you increment I. it should msg an increment. it does in my source.

|

DevelopmentIsMyPassion · Accepted Answer · 2014-01-24 09:51:04Z

0

You need to make module as public. So i suggest below

Public Module Module1
   Public Names() As String
   Public Heights() As Integer
   Public Weights() As Integer
End Module

Then access it in form like

Dim mod1 = Module1
mod1.Names(i) = txtPatientName.Text

answered Jan 24, 2014 at 9:51

DevelopmentIsMyPassion

3,5914 gold badges36 silver badges61 bronze badges

2 Comments

Marcel Over a year ago

I am still receiving the error "'Module1' is a type and cannot be used as an expression"

user2990854 Over a year ago

This was the correct course of action, but the array needed to be "redim preserve" on the event when a record is added.

Collectives™ on Stack Overflow

Object reference not set to instance of an object in VB.NET

2 Answers 2

14 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

14 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related