How to make function work together with Control.CheckForIllegalCrossThreadCalls - vb.net

Question

When I comment Control.CheckForIllegalCrossThreadCalls = False my function works fine but when uncommented it gives an error
I am using a BackgroundWorker to call a function that inserts values into the database and there is a requirement for me to set Control.CheckForIllegalCrossThreadCalls = False in order for the code to work properly. Now when I set it to false one of the functions does not work as expected. Here is the error
Conversion from string "-0-1-22" to type 'Date' is not valid"
yet when that function works fine
Private Sub btnUpload_Click(sender As Object, e As EventArgs) Handles btnUpload.Click
If Not BackgroundWorker1.IsBusy = True Then
BackgroundWorker1.RunWorkerAsync()
End If
End Sub
I expect the function to come up with "2019-06-11" as date to be inserted to the database of which works fine without Control.CheckForIllegalCrossThreadCalls = False
Here is the code
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
count_rows()
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
MsgBox("Products imported successfully!", MsgBoxStyle.Information, "Import")
Me.Close()
End Sub
Public Sub count_rows()
import_attendance_sheet(1054)
End Sub
Private Sub import_attendance_sheet(ByVal id As Integer)
ProgressBar1.Minimum = 0
ProgressBar1.Maximum = id
ProgressBar1.Value = 0
Dim path As String = txtPath.Text
Dim excel_connection As OleDbConnection
Dim dt As DataTable
Dim cmd As OleDbDataAdapter
'Dim sql As String
'Dim result As Boolean
Dim emp_type_id As String = ""
Dim branch_id As String = ""
Dim bank_id As String = ""
'Dim sheet_dates As New List(Of String)
'excel_connection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0; Data Source=" + path + ";Extended Properties=Excel 12.0 Xml; HDR=Yes;")
excel_connection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties='Excel 12.0 Xml;HDR=No;IMEX=1;';")
cmd = New OleDbDataAdapter("SELECT * FROM [sheet$]", excel_connection)
dt = New DataTable
cmd.Fill(dt)
'initialize symbol row
Dim count As Integer = 6
'Loop through dates(column/header)
For Each column As DataColumn In dt.Columns
Dim colum_name As String = dt.Rows(0)(column.ColumnName).ToString()
'check if column cell is empty
If colum_name = "" Then
'Empty do nothing
Else
'increment symbol row by 1
count = count + 1
'MsgBox(count)
'Loop through rows of a particular date/column/header
For Each r As DataRow In dt.Rows
'check row(empNo) cell is not empty & does not have a string
If r(5).ToString() = "" Or r(5).ToString() = "COY #" Then
'Empty do nothing
Else
'show date | Emp No | Name | symbol index
'MsgBox(colum_name & " " & r(5).ToString() & " " & r(6).ToString() & " " & r(count).ToString())
'do the calculation
Dim employ_id As String = get_employee_id(r(5).ToString)
Dim basic_salary As Decimal = get_employee_basic_salary(r(5).ToString)
Dim staff_type_id As String = get_employee_type_id(r(5).ToString)
Dim days_per_month As Integer = get_employee_days_per_month(staff_type_id)
Dim hours_per_day As Double = get_employee_hours_per_day(staff_type_id)
Dim hourly_rate As Double = basic_salary / days_per_month / hours_per_day
Dim daily_rate As Double = basic_salary / days_per_month
Dim normal_working_hrs As String = get_normal_working_hrs()
Dim shift_duration As String = get_shift_duration()
'get symbol id and its rate
Dim symbol_id As String = get_attendance_symbol_id(r(count).ToString)
Dim symbol_rate As Double = get_attendance_symbol_rate(symbol_id)
Dim symbol_deduction_status As String = get_symbol_deduction_status(symbol_id)
Dim td_amount As Double = 0
If symbol_deduction_status = "DEDUCT" Then
td_amount = hourly_rate
Else
td_amount = 0
End If
Dim overtime As Double = shift_duration - normal_working_hrs
Dim ot_amount As Double = overtime * hourly_rate * symbol_rate
Dim chaka As String = Date.Now.ToString("yyyy")
Dim tsiku As String = Date.Now.ToString("dd")
Dim tsiku_mawu As String = Date.Now.ToString("dddd")
Dim mwezi As String = Date.Now.ToString("MMMM")
' ''insert values into DB
Sql = "INSERT INTO tbl_attendance (employee_id,time_in,time_out,total_hours_worked,overtime,ot_amount,td_amount,attendance_code_id,attendance_code,attendance_date,comment,year,date,day,month,hourly_rate,bsalary,ot_status) VALUES ('" & employ_id & "','" & 0 & "','" & 0 & "','" & shift_duration & "','" & overtime & "','" & ot_amount & "','" & td_amount & "','" & symbol_id & "','" & r(count).ToString & "','" & calc_attendance_date(colum_name) & "','import','" & chaka & "','" & tsiku & "','" & tsiku_mawu & "','" & mwezi & "','" & hourly_rate & "','" & basic_salary & "','" & symbol_rate & "')"
result = save_to_db(Sql)
ProgressBar1.Value = ProgressBar1.Value + 1
'If result Then
' Timer1.Start()
'End If
End If
Next
End If
Next
End Sub
'******* Function which shows the error ****************
Public Function calc_attendance_date(ByVal value As String)
Dim at_date As String = ""
Dim current_month As String = frmMain.cmbMonth.Text
Dim current_year As String = frmMain.cmbYear.Text
Dim mwezi As String
Dim chaka As String
Dim format_day As String = ""
Dim format_month As String = ""
'Date.Now.ToString("yyyy-MM-dd")
'**** find previous month
'when its january
If current_month = "January" And value >= 22 And value <= 31 Then
mwezi = "12"
chaka = Convert.ToInt32(current_year) - 1
at_date = chaka & "-" & mwezi & "-" & value
ElseIf current_month <> "January" And value >= 22 And value <= 31 Then
mwezi = IntMonth() - 1
'day
If value < 10 Then
format_day = "0" & value
ElseIf value >= 10 Then
format_day = value
End If
'format mwezi
If mwezi < 10 Then
format_month = "0" & mwezi
ElseIf mwezi >= 10 Then
format_month = mwezi
End If
chaka = current_year
at_date = chaka & "-" & format_month & "-" & format_day
End If
'**** find current month
If current_month = "January" And value >= 1 And value <= 21 Then
mwezi = IntMonth()
chaka = current_year
'day
If value < 10 Then
format_day = "0" & value
ElseIf value >= 10 Then
format_day = value
End If
'format mwezi
If mwezi < 10 Then
format_month = "0" & mwezi
ElseIf mwezi >= 10 Then
format_month = mwezi
End If
at_date = chaka & "-" & format_month & "-" & format_day
ElseIf current_month <> "January" And value >= 1 And value <= 21 Then
mwezi = IntMonth()
chaka = current_year
'day
If value < 10 Then
format_day = "0" & value
ElseIf value >= 10 Then
format_day = value
End If
'format mwezi
If mwezi < 10 Then
format_month = "0" & mwezi
ElseIf mwezi >= 10 Then
format_month = mwezi
End If
at_date = chaka & "-" & format_month & "-" & format_day
End If
Return at_date
End Function

Answer 1

You shouldn't try to interact with UI controls from a non-UI thread. You can however have code which interacts with those controls on a UI thread by using Control.Invoke. There are a few places where you do it.
Inside import_attendance_sheet
ProgressBar1.Minimum = 0
ProgressBar1.Maximum = id
ProgressBar1.Value = 0
Dim path As String = txtPath.Text
...
ProgressBar1.Value = ProgressBar1.Value + 1
Instead:
Dim path As String
Me.Invoke(
Sub()
ProgressBar1.Minimum = 0
ProgressBar1.Maximum = id
ProgressBar1.Value = 0
path = txtPath.Text
End Sub)
...
Me.Invoke(Sub() ProgressBar1.Value += 1)
All those functions like get_employee_id, get_employee_basic_salary, get_employee_type_id may also interact with the UI, but you don't provide them. If they do (i.e. return a value from a textbox or something) then you need to invoke inside them as well.
Inside calc_attendance_date
Dim current_month As String = frmMain.cmbMonth.Text
Dim current_year As String = frmMain.cmbYear.Text
Instead:
Dim current_month As String
Dim current_year As String
Me.Invoke(
Sub()
current_month = frmMain.cmbMonth.Text
current_year = frmMain.cmbYear.Text
End Sub)
The function IntMonth() is unknown to us too. Again, if it reads from the UI you should invoke the code which does the UI interaction.
The correct way to do this is only invoke when absolutely necessary, i.e. when Control.InvokeRequired. See this example which is very close to yours in that they wanted to use Me.CheckForIllegalCrossThreadCalls = False (BAD!)
Even better, you can write extension methods to automate the Control.InvokeRequired pattern