No Longer "Quick Question"........Accessing controls on the main form from a CLASS,

Hi guys,

I have a problem .....

In my module,

VB Code:

Imports System.IO
 
Module mod_Maths_Functions
    Public CRSC As CRS_Creator.frmMain
 
    Function DeviationCalculation()
        Dim sWriter As StreamWriter
        Dim strTemp As String
        Dim arrTemp(19) As Double
        Dim arrDev As Array
        Dim i, j As Integer
 
        'This bit is to create two file in the temp directory for use, then store the name of the file for
        'furture ADO.Net Use.
        tempFileBaseLoad = CreateTempFile()  'create a new temp file for use....
        FileBaseLoadname = tempFileBaseLoad.Substring(tempPathString.Length, tempFileBaseLoad.Length - tempPathString.Length)
        tempFileMSG = CreateTempFile() 'create a new temp file for use....
        FileMSGname = tempFileMSG.Substring(tempPathString.Length, tempFileMSG.Length - tempPathString.Length)
 
 
        'Need to delete the old files if they exist
        Try
            If IO.File.Exists(tempFileBaseLoad) = True Then
                File.Delete(tempFileBaseLoad)
            End If
            If IO.File.Exists(tempFileMSG) = True Then
                File.Delete(tempFileMSG)
            End If
        Catch ex As Exception
        End Try
        sWriter = IO.File.CreateText(tempFileBaseLoad)
        sWriter.WriteLine("Time,GTload,Dev1,Dev2,Dev3,Dev4,Dev5,Dev6,Dev7,Dev8,Dev9,Dev10,Dev11,Dev12,Dev13,Dev14,Dev15,Dev16,Dev17,Dev18")
        sWriter.Close()
        sWriter = IO.File.CreateText(tempFileMSG)
        sWriter.WriteLine("Time,GTload,Dev1,Dev2,Dev3,Dev4,Dev5,Dev6,Dev7,Dev8,Dev9,Dev10,Dev11,Dev12,Dev13,Dev14,Dev15,Dev16,Dev17,Dev18")
        sWriter.Close()
        Dim progressCounter, progressIncrement As Single
        progressIncrement = 100 / dt.Rows.Count
        Dim prog As ProgressBar
        prog = CRSC.progBar1
 
 
        For j = 1 To dt.Rows.Count - 1
            Application.DoEvents()
            For i = 0 To 19
                arrTemp(i) = dt.Rows(j)(i)
            Next
            strTemp = CanDeviation(arrTemp)
            If arrTemp(1) >= 200 Then    'checks if it is at baseload
                sWriter = IO.File.AppendText(tempFileBaseLoad)
            Else
                sWriter = IO.File.AppendText(tempFileMSG)
            End If
            sWriter.WriteLine(strTemp)
            sWriter.Close()
            progressCounter += progressIncrement
            prog.Value = progressCounter
        Next
 
    End Function
    Function CanDeviation(ByRef arrInput As Array) As String
        Dim i As Integer
        Dim arrOutput(19) As Single
        Dim sngCanTempSum As Single
        Dim sngCanAverage As Single
        Dim strTemp As String
 
 
        For i = 2 To 19
            sngCanTempSum += arrInput(i)
        Next
 
        'Now we have the total can Temp
        sngCanAverage = sngCanTempSum / 18
        'Divide by 18 to get can average temp
 
        For i = 0 To 1  'Put the Time and GTload back in
            arrOutput(i) = arrInput(i)
        Next
 
        For i = 2 To 19 'Now get the deviation from mean
            arrOutput(i) = ((arrInput(i) - sngCanAverage) / sngCanAverage) * 100
        Next
 
        For i = 0 To arrOutput.Length - 1
            strTemp &= arrOutput(i) & ","
        Next
        Return strTemp
    End Function
End Module

I have a progressBar which is called progBar1 on the frmMain and i need to access it from my module. However, it throws up the following error,

VB Code:

An unhandled exception of type 'System.NullReferenceException' occurred in CRS Creator.exe
 
Additional information: Object reference not set to an instance of an object.

Any ideas? I know i can pass the control from the main form when i call up the function ..

ummm the is a problem i wand help you real but i have 1 script that only is to use you progbar sorry

No probs buddy

Thanks for the reply anyway :) :thumb:

;) np

Hi Dino
You forgot the new on your DeviationCalculation function.

VB Code:

Dim prog As ProgressBar

Regards
Jorge

Yeha that is on the main form...

i have no problems with progBar ....just with progBar1 coz i am calling it from the module...

:(

haven't you forgotten to set CRSC before calling the sub in this module. Anyways wouldn't it be better to move all this into a class instead of a module?

Why would it be better in a class?

if you put it in a class , you can add a reference to your Form ( because it's a null object at present ) , eg:

VB Code:

Public Class mod_Maths_Functions
 
    Public CRSC As CRS_Creator.frmMain
    
    Public Sub New(frm As Form)
        CRSC = DirectCast( frm , CRS_Creator.frmMain )
        '/// Now CRSC is an Active Reference to CRS_Creator.frmMain 
    End Sub
 
'/// Rest of Your Code Here ...
 
End Class

to access from a Form / Class ...

VB Code:

Dim cls As New mod_Maths_Functions( Me ) '/// Where Me = the name of the Calling Form ( ie: CRS_Creator.frmMain )

I believe, although not sure if it is considered good coding practice, you can pass the Form through your function and access all of its members (much like a class) through a function/sub in a module.

Code:

---

Public Sub ClearComboBox(frm As Form1)
  frm.ComboBox1.Items.Clear()
End Sub

---

Not at a machine to test but I am pretty sure it will work.

EDIT: You might need to pass the frm parameter ByRef rather than ByVal for it to work but I am not sure. If the default (ByVal) doesn't work you can always change it to ByRef and try

So a module is essentially a classed which is shared, so why does it have to be a class and not a module?

it seems more complicated....

Quote:

---

Originally Posted by dynamic_sysop

if you put it in a class , you can add a reference to your Form ( because it's a null object at present ) , eg:

VB Code:

Public Class mod_Maths_Functions
 
    Public CRSC As CRS_Creator.frmMain
    
    Public Sub New(frm As Form)
        CRSC = DirectCast( frm , CRS_Creator.frmMain )
        '/// Now CRSC is an Active Reference to CRS_Creator.frmMain 
    End Sub
 
'/// Rest of Your Code Here ...
 
End Class

to access from a Form / Class ...

VB Code:

Dim cls As New mod_Maths_Functions( Me ) '/// Where Me = the name of the Calling Form ( ie: CRS_Creator.frmMain )

---

Why does a class accept a sub but not a module???

Quote:

---

Originally Posted by dinosaur_uk

Why does a class accept a sub but not a module???

---

What do you mean?

A module can have a sub just not a Sub New().

modules were put into vb.net to keep the vb6ers happy... as such they may be removed in future versions. Classes are more powerful and you can use them in the same way if you add shared to your property/function/sub/variable

VB.NET is a fully OOP (Object Oriented Programing) language. you should be using OOP properly.

Cheers guys....

I will start using classes from now onwards....


Cheers