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

#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.Cursor.Current = Cursors.WaitCursor
        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(SQLString, dbConnection)
        cmdCourses.CommandType = CommandType.Text
        rsCourses = cmdCourses.ExecuteReader
 
        frmCourses.lvwCourses.Items.Clear()
        While rsCourses.Read
            adItem = frmCourses.lvwCourses.Items.Add(rsCourses(0), 0)   'Course ID
            adItem.SubItems.Add(rsCourses(1))                           'Title
            adItem.SubItems.Add(rsCourses(2))                           'Description
        End While
 
        frmCourses.lblTotalRecords.Text = "Total Records: " & frmCourses.lvwCourses.Items.Count
 
        If frmCourses.lvwCourses.Items.Count > 0 Then
            frmCourses.lblShowStatus.Visible = False
        Else
            frmCourses.lblShowStatus.Visible = True
        End If
 
        For i = 0 To frmCourses.lvwCourses.Items.Count - 1
            If ModColor = True Then
                frmCourses.lvwCourses.Items(i).BackColor = Color.AliceBlue
                ModColor = False
            Else
                frmCourses.lvwCourses.Items(i).BackColor = Color.White
                ModColor = True
            End If
        Next
 
        rsCourses.Close()
        Call CloseConnection()
        Windows.Forms.Cursor.Current = Cursors.Default
    End Sub

frmCourses

Private Sub txtSearch_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtSearch.TextChanged
        Transaction.Courses.Show(False, txtSearch.Text)
    End Sub
 
Private Sub frmCourses_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Main.SetChildForm(frmMain, Me)
        Transaction.Courses.Show(True)
    End Sub
 

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?