Object reference not set to an instance of an object.

**kenobewan** · Oct 22 '08, 12:07 PM

It would help if you could provide more information. Do you have a line number where it is occurring or can you trap it?

**Abhiraj Chauhan** · Oct 23 '08, 06:46 AM

Well thanks for replying....... .Actually in my project i have 2 forms one consist of a datagrid and other form consisting of a picture box,,,,,and now when you enter data in first form you can see the drawing of your data in the other form.

also i am using vb.net for first time so if u can help me what should i use for drawing lines ...... system.drawing. graphics or system.windows. forms.paintEven targs

**tlhintoq** · Oct 23 '08, 07:32 AM

Originally posted by Abhiraj Chauhan

I am trying to draw line.....Actual ly these codes were previously in vb 6...i tried to change them in vb.net....but every time i try to run the application i got this error ."Object reference not set to an instance of an object"...plz help me regerding this error....here are my code

Code:

Sub BeamDraw(ByRef DrawControl As PaintEventArgs, ByRef ds As DAO.Recordset)
        Dim Y5 As Double
        Dim X5 As Double
        Dim Y2 As Double
        Dim X2 As Double
        Dim Y3 As Double
        Dim X3 As Double
        Dim Y1 As Double
        Dim X1 As Double
        Dim szcolumn As String
        Dim X As Single
        Dim Y As Single
        Dim Dc As DAO.Recordset
        Dim DCC As DAO.Recordset
        DCC = CurDb.OpenRecordset("Columns", DAO.RecordsetTypeEnum.dbOpenDynaset)
        Dc = CurDb.OpenRecordset("Columns", DAO.RecordsetTypeEnum.dbOpenDynaset)
        While Not ds.EOF
            szcolumn = "Cname='" + ds.Fields(0).Value + "'"
            DCC.FindFirst(szcolumn)
            X = DCC.Fields(4).Value
            Y = DCC.Fields(5).Value
            X1 = DCC.Fields(4).Value
            Y1 = DCC.Fields(5).Value
            FlushDistances(DCC, X, Y)
            X3 = X
            Y3 = Y
            If StrComp(Left(DCC.Fields(0).Value, 1), "C") = 0 Then
                Select Case DCC.Fields(1).Value
                    Case "H"
                        DrawControl.Graphics.DrawLine(Pens.OrangeRed, CInt(X - DCC.Fields(2).Value / 2), CInt(Y - DCC.Fields(3).Value / 2) - CInt(X + DCC.Fields(2).Value / 2), CInt(Y + DCC.Fields(3).Value / 2), B)
                        
                 
                End Select
            Else
                Select Case DCC.Fields(1).Value
                    Case "H"              
                        DrawControl.Graphics.DrawLine(Pens.OrangeRed, CInt(X - DCC.Fields(2).Value / 2), CInt(Y - DCC.Fields(3).Value / 2) - CInt(X + DCC.Fields(2).Value / 2), CInt(Y + DCC.Fields(3).Value / 2), B)
                  
                End Select
            End If
            If Enlarge Or BeamSelect Then
                Column_Dis(DCC.Fields(4).Value + DCC.Fields(2).Value / 2, DCC.Fields(5).Value - DCC.Fields(3).Value / 2, DCC.Fields(0).Value, DrawControl)
            End If
            szcolumn = "Cname='" + ds.Fields(1).Value + "'"
            Dc.FindFirst(szcolumn)
            X = (Dc.Fields(4).Value)
            Y = (Dc.Fields(5).Value)
            X2 = Dc.Fields(4).Value
            Y2 = Dc.Fields(5).Value
            FlushDistances(Dc, X, Y)
            X5 = X
            Y5 = Y
            If X1 = X2 Then
                CenterFlag = "BeamVertical"
            Else
                If Y1 = Y2 Then
                    CenterFlag = "BeamHorizontal"
                End If
            End If
            If StrComp(Left(Dc.Fields(0).Value, 1), "C") = 0 Then
                Select Case Dc.Fields(1).Value
                    Case "H"
                        DrawControl.Graphics.DrawLine(Pens.OrangeRed, CInt(X - Dc.Fields(2).Value / 2), CInt(Y - Dc.Fields(3).Value / 2), CInt(X + Dc.Fields(2).Value / 2), CInt(Y + Dc.Fields(3).Value / 2))
                                                  
                End Select
            Else
                Select Case Dc.Fields(1).Value
                    Case "H"
                       
                        DrawControl.Graphics.DrawLine(Pens.OrangeRed, CInt(X - Dc.Fields(2).Value / 2), CInt(Y - Dc.Fields(3).Value / 2) - CInt(X + Dc.Fields(2).Value / 2), CInt(Y + Dc.Fields(3).Value / 2), B)
                      
                End Select
            End If

            If Enlarge Or BeamSelect Then
                Column_Dis(Dc.Fields(4).Value + Dc.Fields(2).Value / 2, Dc.Fields(5).Value - Dc.Fields(3).Value / 2, Dc.Fields(0).Value, DrawControl)
            End If
            ShowBeam(ds, DCC, DCC, DrawControl, X3, Y3, X5, Y5, CenterFlag)
            ds.MoveNext()
        End While
    End Sub

Total stab in the dark by someone who doesn't do VB...

In line 78 you make use of CenterFlag variable.
I see no place where you create this variable (Looks like that is done with the DIM statement as in line 10 ??)

Assuming this is a global variable created elsewhere... Is it ever initialized to a default value? CenterFlag only gets set in Verticle in line 54 if X1=X2 or to Horizontal in line 57 if Y1=Y2. What happens if neither of these conditions exist? Does CenterFlag remain unset later when it is used in line 78?

**r035198x** · Oct 23 '08, 07:42 AM

Originally posted by Abhiraj Chauhan

Well thanks for replying....... .Actually in my project i have 2 forms one consist of a datagrid and other form consisting of a picture box,,,,,and now when you enter data in first form you can see the drawing of your data in the other form.

also i am using vb.net for first time so if u can help me what should i use for drawing lines ...... system.drawing. graphics or system.windows. forms.paintEven targs

Why don't you just tell us the number reported for that exception?

**Abhiraj Chauhan** · Oct 24 '08, 10:22 AM

Originally posted by tlhintoq

Total stab in the dark by someone who doesn't do VB...

In line 78 you make use of CenterFlag variable.
I see no place where you create this variable (Looks like that is done with the DIM statement as in line 10 ??)

Assuming this is a global variable created elsewhere... Is it ever initialized to a default value? CenterFlag only gets set in Verticle in line 54 if X1=X2 or to Horizontal in line 57 if Y1=Y2. What happens if neither of these conditions exist? Does CenterFlag remain unset later when it is used in line 78?

Then it Will give us a diagonal Connection....W ell Thank u .....

Object reference not set to an instance of an object.

Object reference not set to an instance of an object.

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