Invalid Operation Exception was unhandled

[lotus18]

WaAh!

My form was working fine earlier but later it displays Invalid Operation Exception was unhandled. I don't know what's wrong with my form every time I load it.I checked its codes but I find what's wrong with it.

If I'm going to remove Transaction.Cou rses.Show(False , txtSearch.Text) at line #2 of frmCourses it works fine. Of course I cannot filter the records : (

This is my sample codes

clsCourses
[CODE=vbnet]
#Region " Variable Declarations... "
Private ModColor As Boolean
Private SQLString As String
Private i As Integer
Private adItem As ListViewItem
Private rsCourses As OleDbDataReader
Private cmdCourses As New OleDbCommand
#End Region

Public Sub Show(ByVal ShowAllList As Boolean, Optional ByVal Search As String = vbNullString)
Windows.Forms.C ursor.Current = Cursors.WaitCur sor
If ShowAllList Then
SQLString = "Select * From Courses Order By Title ASC"
Else
SQLString = "Select * From Courses Where CourseID Like '%" & Search & _
"%' Or Title Like '%" & Search & "%' Or Description Like '%" & _
Search & "%' Order By Title ASC"
End If

Call SetConnection()
cmdCourses = New OleDbCommand(SQ LString, dbConnection)
cmdCourses.Comm andType = CommandType.Tex t
rsCourses = cmdCourses.Exec uteReader

frmCourses.lvwC ourses.Items.Cl ear()
While rsCourses.Read
adItem = frmCourses.lvwC ourses.Items.Ad d(rsCourses(0), 0) 'Course ID
adItem.SubItems .Add(rsCourses( 1)) 'Title
adItem.SubItems .Add(rsCourses( 2)) 'Description
End While

frmCourses.lblT otalRecords.Tex t = "Total Records: " & frmCourses.lvwC ourses.Items.Co unt

If frmCourses.lvwC ourses.Items.Co unt > 0 Then
frmCourses.lblS howStatus.Visib le = False
Else
frmCourses.lblS howStatus.Visib le = True
End If

For i = 0 To frmCourses.lvwC ourses.Items.Co unt - 1
If ModColor = True Then
frmCourses.lvwC ourses.Items(i) .BackColor = Color.AliceBlue
ModColor = False
Else
frmCourses.lvwC ourses.Items(i) .BackColor = Color.White
ModColor = True
End If
Next

rsCourses.Close ()
Call CloseConnection ()
Windows.Forms.C ursor.Current = Cursors.Default
End Sub[/CODE]
frmCourses
[CODE=vbnet]Private Sub txtSearch_TextC hanged(ByVal sender As System.Object, ByVal e As System.EventArg s) Handles txtSearch.TextC hanged
Transaction.Cou rses.Show(False , txtSearch.Text)
End Sub

Private Sub frmCourses_Load (ByVal sender As System.Object, ByVal e As System.EventArg s) Handles MyBase.Load
Main.SetChildFo rm(frmMain, Me)
Transaction.Cou rses.Show(True)
End Sub
[/CODE]

Rey Sean

[kenobewan]

An integer, eg an id, can't be like another incl in an sql statement. Suggest using try catch blocks and/ or other error handling. HTH.

[lotus18]

An integer, eg an id, can't be like another incl in an sql statement. Suggest using try catch blocks and/ or other error handling. HTH.

Hi

Thanks for your reply : )

I've used try and catch blocks as what you've said but still it gives me an error result, An error occurred creating the form. See Exception.Inner Exception for details. The error is: The form referred to itself during construction from a default instance, which led to infinite recursion. Within the Form's constructor refer to the form using 'Me.'

BTW, what do you mean by incl?

Rey Sean

[Plater]

Well what I saw turned out to be exactly what the error was giving you. So I think I am right on this.

In your form_load function (which gets called everytime it's shown) you are trying to SHOW it again. Which would lead to infinite recurrsion.
Remove the unneeded .Show() call like you said to make it work.
It shouldn't be there anyway.

[lotus18]

Well what I saw turned out to be exactly what the error was giving you. So I think I am right on this.

In your form_load function (which gets called everytime it's shown) you are trying to SHOW it again. Which would lead to infinite recurrsion.
Remove the unneeded .Show() call like you said to make it work.
It shouldn't be there anyway.

If that is the reason I think I should create another method for clsCourses for filtering the records. But I don't think that is the best idea because I am going to create another method again with almost the same as with the showing of records the only difference between them is their sql statement. Can you give me another idea how to handle this?

Rey Sean

[Plater]

Well lets start off with why are you continuing to make another instance of your class? (Or at least calling Show many times)
If you want to hide the form and then unhide it, use the Visible property?