Blocking the user in Exit which is not already Logged in at the Entrance

Good Day, I need help for my vb.net application which is using RFID reader rc522 and arduino Uno, all is well and already functioning regarding the card scanning. When the card is scanned the data from the database will be retrieve and show to the interface screen, I have 2 RFID which is located in separated doors, ENTRANCE and EXIT and 1 server database to save the logged in students and out..Now the problem is when the student don't scan his/her RFID card in the entrance , the error will show in the EXIT interface when the student scan his Id in the EXIT. Is there any way to block the student who are not scanning his rfid in the entrance to the exit ? Thank you This is my code



Private Sub Students_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

loadtable()
''Date Now
Timer2.Start()

logins.ForeColor = Color.White
Try

With DataGridView1
.AllowUserToAddRows = False ' Disabled or hide (*) Symbol...

.RowHeadersVisible = False 'To hide Left indicator..
.DefaultCellStyle.SelectionBackColor = Color.SteelBlue 'Selection backcolor....
.AlternatingRowsDefaultCellStyle.BackColor = Color.LightGoldenrodYellow 'Alternating Backcolor.
.AllowUserToResizeRows = False 'Disabled row resize...
.ReadOnly = True
.MultiSelect = False
.SelectionMode = DataGridViewSelectionMode.FullRowSelect
.ShowRowErrors = False
.ShowCellErrors = False
.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill


End With



Catch ex As Exception

End Try



''The combobox filled with serial ports available

comPORT = ""
For Each sp As String In My.Computer.Ports.SerialPortNames
comPort_ComboBox.Items.Add(sp)
Next
''Paglalagay ng collections



End Sub

''FFor Replacing the textbox for a new card

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived

Dim StringIn As String = SerialPort1.ReadLine()
StringIn = StringIn.Replace(Chr(10), "").Replace(Chr(13), "")
Me.Invoke(Sub() studtag.Text = StringIn) 'we need to invoke since we're on another thread




End Sub

Public Sub insert()

con = New MySqlConnection
con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
Dim reader As MySqlDataReader
Dim mstream As New System.IO.MemoryStream()

Dim arrImage() As Byte = mstream.GetBuffer()
mstream.Close()

Try

con.Open()
Dim query3 As String

query3 = "insert into dat.studlogs (studtags,idno,lastxt,firstxt,middletxt,dob,log,timein,crse,studpic) values ('" & tagtxt.Text & "','" & idno.Text & "','" & lastxt.Text & "','" & firstxt.Text & "','" & middletxt.Text & "','" & dob.Text & "','" & log.Text & "','" & timein.Text & "','" & crsetxt.Text & "',@studpic)"
cmd = New MySqlCommand(query3, con)
cmd.Parameters.AddWithValue("@studpic", arrImage)
reader = cmd.ExecuteReader


con.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
con.Dispose()
End Try

End Sub
Public Sub loadtable()



con = New MySqlConnection
con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
Dim SDA As New MySqlDataAdapter
Dim dbDataset As New DataTable
Dim bSource As New BindingSource


Try

con.Open()
Dim query3 As String

query3 = "select idno as 'Student_ID',lastxt as 'LastName',firstxt as 'FirstName',middletxt as 'MiddleName',log as 'Status',timein as 'Timein',crse as 'Course' from dat.studlogs"
cmd = New MySqlCommand(query3, con)
SDA.SelectCommand = cmd
SDA.Fill(dbDataset)
bSource.DataSource = dbDataset
DataGridView1.DataSource = bSource
SDA.Update(dbDataset)

DataGridView1.Sort(DataGridView1.Columns(5), System.ComponentModel.ListSortDirection.Descending)


If dbDataset.Rows.Count > 0 Then
logins.Text = dbDataset.Rows.Count.ToString()
End If


con.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
con.Dispose()
End Try
End Sub

Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
bday.Text = Date.Now.ToString("MMMM d")
datenow.Text = Date.Now.ToString("MMMM d, yyyy")
times.Text = TimeOfDay.ToString("h:mm:ss tt")
wholedate.Text = Now
End Sub


''Here is the Scanning

Private Sub studtag_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles studtag.TextChanged

Notenrolled.Close()
greet.Text = ""
PictureBox4.Visible = False

If studtag.Text = "44F2F38B" Then

Endday()

End If

If studtag.TextLength = 8 Then

DataGridView1.Sort(DataGridView1.Columns(6), System.ComponentModel.ListSortDirection.Descending)
con = New MySqlConnection
con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
Dim query As String

query = "select * from dat.students"
cmd = New MySqlCommand(query, con)



Dim table As New DataTable

Try
con.Open()
'Gets or sets an SQL statement or stored procedure used to select records in the database.
With cmd
.Connection = con
.CommandText = "SELECT * from students where `studtags`='" & studtag.Text & "';"
End With
da.SelectCommand = cmd
da.Fill(table)
'it gets the data from specific column and fill it into Label

idno.Text = table.Rows(0).Item(1)
lastxt.Text = table.Rows(0).Item(2)
firstxt.Text = table.Rows(0).Item(3)
middletxt.Text = table.Rows(0).Item(4)
dob.Text = table.Rows(0).Item(6)
year.Text = table.Rows(0).Item(7)
crsetxt.Text = table.Rows(0).Item(10)

tagtxt.Text = studtag.Text
timein.Text = times.Text

dr = cmd.ExecuteReader()
dr.Read()

If dob.Text = bday.Text Then
greet.Text = firstxt.Text + " Today is your Birthday. Greetings :D."
PictureBox4.Visible = True

End If



Dim img() As Byte = CType(dr("studpic"), Byte())


Using ms As New IO.MemoryStream(img)
PictureBox1.Image = Image.FromStream(ms)

End Using
insert()
loadtable()
studdailyhistory()


Catch ex As Exception
Notenrolled.Show()
DataGridView1.Sort(DataGridView1.Columns(5), System.ComponentModel.ListSortDirection.Descending)
If studtag.Text = "44F2F38B" Then
Notenrolled.Close()
End If

Finally

con.Dispose()
con.Close()

End Try

End If

End Sub

The Out code is almost the same as IN. Thank you. Ask me anything if you have questions about this..Any Advice and answers is so much appreciated..Save me for my final defense.
The Problem with this, is when the students left their RFID card and make a way to get inside the university except in ENTRANCE GATE due to no Card to scan

There's really way too much code there. Please only post the RELEVANT code. Also, please use formatting tags when posting code, i.e.

[HIGHLIGHT=vb.net]your code here[/HIGHLIGHT]

or

[CODE]your code here[/CODE]

You didn't say which line of code was throwing the error, I'm guessing this one.

Code:

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idno.Text = table.Rows(0).Item(1)

---

The problem is your assuming that

Code:

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"SELECT * from students where `studtags`='" & studtag.Text & "';"

---

Will return a row of data.

It's easy enough to test "If table.rows.Count > 0 Then ....."

Hello Thank you for that. But i have no problem with the code I just need a additional code for this problem..

Quote:

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Originally Posted by jmcilhinney

There's really way too much code there. Please only post the RELEVANT code. Also, please use formatting tags when posting code, i.e.

[HIGHLIGHT=vb.net]your code here[/HIGHLIGHT]

or

[CODE]your code here[/CODE]

---

Hello Thank you for that. But i have no problem with the code I just need a additional code for this problem..

Quote:

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Originally Posted by sangguko19

Hello Thank you for that. But i have no problem with the code I just need a additional code for this problem..

---

I showed you how to solve the problem.

Quote:

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Originally Posted by sangguko19

Hello Thank you for that. But i have no problem with the code I just need a additional code for this problem..

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Why did you post a large block of unformatted code if it has no relevance?