DataGridView select multiple row, check each row - mysql

Question

I am trying to select all rows by a button or select different rows with ctrl+click.
But even if I have selected multiple rows, it only checks the first row. Then it rereads it again instead of going to the next row.
I'm not sure either where to put the multiselect code.
Originally, you're only supposed to just click a row then check if conditions are satisfied. However it was requested that you can do multiple and check each row if condition is satisfied.
Here is my code:
Private Sub DataGridView1_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DataGridView1.SelectionChanged
Dim i As Integer
i = DataGridView1.CurrentRow.Index
_subjectno = DataGridView1.Item(0, i).Value
_title = DataGridView1.Item(1, i).Value
_unit = DataGridView1.Item(2, i).Value
_pre = DataGridView1.Item(3, i).Value
End Sub
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
DataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect
DataGridView1.MultiSelect = True
DataGridView1.SelectAll()
End Sub
Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
Dim selectedItems As DataGridViewSelectedRowCollection = DataGridView1.SelectedRows
For Each selectedItem As DataGridViewRow In selectedItems
add()
Next
End Sub
Sub add()
Try
If IS_EMPTY(txtSno) = True Then Return
cm = New MySqlCommand("select * from tblenroll where subjectnumber like '" & _subjectno & "' and remarks <> 'Failed' and studentno like '" & txtSno.Text & "'", cn)
dr = cm.ExecuteReader
dr.Read()
If dr.HasRows Then
MsgBox("Subject is already taken.", vbExclamation)
dr.Close()
Return
Else
dr.Close()
End If
If _pre = "NONE" Or _pre = "2ND YR STANDING" Or _pre = "3RD YR STANDING" Or _pre = "4TH YR STANDING" Or _pre = "5TH YR STANDING" Then
cm = New MySqlCommand("insert into tblenroll (studentno, subjectnumber, ay,semester,dateenrolled, curriculum) values ('" & txtSno.Text & "','" & _subjectno & "','" & txtAY.Text & "','" & txtSem.Text & "','" & Now & "','" & txtCurriculum.Text & "')", cn)
cm.ExecuteNonQuery()
MsgBox(_subjectno & " successfully added.", vbInformation)
LoadEnrolled()
Else
cm = New MySqlCommand("select * from tblenroll where studentno like '" & txtSno.Text & "' and subjectnumber like '" & _subjectno & "' and ay like '" & txtAY.Text & "'", cn)
dr = cm.ExecuteReader
dr.Read()
If dr.HasRows Then
MsgBox("Subject is already taken.", vbExclamation)
dr.Close()
Return
Else
dr.Close()
End If
Dim strok As Boolean = False
Dim strArr() As String
Dim count As Integer
Dim strpre As String = _pre
strArr = strpre.Split(", ")
For count = 0 To strArr.Length - 1
cm = New MySqlCommand("select * from tblenroll as e inner join tblsubject as s on e.subjectnumber = s.subjectno where s.subjectno like '%" & Trim(strArr(count)) & "%' and studentno like '" & txtSno.Text & "' and remarks like 'Passed'", cn)
dr = cm.ExecuteReader
dr.Read()
If dr.HasRows Then
dr.Close()
strok = True
Else
MsgBox("Unable to enroll this subject. Pre-requisite " & strArr(count) & ".", vbExclamation)
dr.Close()
Return
End If
Next
If strok = True Then
cm = New MySqlCommand("insert into tblenroll (studentno, subjectnumber, ay, semester, dateenrolled, curriculum) values ('" & txtSno.Text & "','" & _subjectno & "','" & txtAY.Text & "','" & txtSem.Text & "','" & Now & "','" & txtCurriculum.Text & "')", cn)
cm.ExecuteNonQuery()
MsgBox(_subjectno & " successfully added.", vbInformation)
LoadEnrolled()
End If
End If
Catch ex As Exception
MsgBox(ex.Message, vbCritical)
End Try
End Sub
Thank you so much!

Answer 1

Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
For Each selectedItem As DataGridViewRow In DataGridView1.SelectedRows
_subjectno = selectedItem.Cells(0).Value
_title = selectedItem.Cells(1).Value
_unit = selectedItem.Cells(2).Value
_pre = selectedItem.Cells(3).Value
add()
Next
End Sub