ArgumentOutOfRangeException was Unhandled , Index was out of range - vb.net

Question

I want to ask if anyone knows this why this error occurs? So there are 2 forms. The first calculation form there is no error and this is the second calculation form which produces the error, after searching here and there masi not yet enlightenment, maybe someone can help?
THIS SCREENSHOT OF ERROR
this full source code
Public Class FrmHitung2
Private Sub FrmHitung2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim dt As DataTable = openDT("SELECT * FROM tb_rel_alternatif2 WHERE kode_crips NOT IN (SELECT kode_crips FROM tb_crips2)")
If dt.Rows.Count > 0 Then
msgError("Anda belum mengatur nilai untuk setiap alternatif, silahkan atur di menu Nilai Bobot")
BtnCetak.Enabled = False
Else
Dgv1.AllowUserToAddRows = False
Dgv1.AllowUserToDeleteRows = False
Dgv1.ReadOnly = True
Dgv1.AutoGenerateColumns = False
awal()
End If
End Sub
Sub awal()
Dgv1.Columns.Clear()
Dgv1.Rows.Clear()
Dgv1.Columns.Add("nim", "Kode")
Dgv1.Columns("nim").ReadOnly = True
Dgv1.Columns.Add("nama_mahasiswa", "Nama")
Dgv1.Columns("nama_mahasiswa").ReadOnly = True
dr = openDR("SELECT * FROM tb_alternatif2 ORDER BY nim")
While dr.Read()
Dgv1.Rows.Add(dr(0), dr(1))
End While
dr = openDR("SELECT kode_kriteria, atribut FROM tb_kriteria2 ORDER BY kode_kriteria")
While dr.Read()
Dgv1.Columns.Add(dr(0), dr(0))
Dgv1.Columns(dr(0).ToString()).ToolTipText = dr(1).ToString()
End While
For a = 0 To Dgv1.Rows.Count - 1
dr = openDR("SELECT c.nama_crips FROM tb_rel_alternatif2 r " &
" LEFT JOIN tb_crips2 c ON c.kode_crips = r.kode_crips " &
" WHERE nim='" & Dgv1.Rows(a).Cells(0).Value & "' ORDER BY r.kode_kriteria")
Dim b As Integer = 2
While dr.Read
Dgv1.Rows(a).Cells(b).Value = dr(0)
b = b + 1
End While
Next
Dgv1.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.AllCells
BtnCetak.Enabled = False
End Sub
Function get_col_max(ByVal dgv As DataGridView, ByVal col_name As String) As Double
Dim max As Double = 0
If dgv.Rows.Count > 0 Then max = Val(dgv.Rows(0).Cells(col_name).Value)
For Each row As DataGridViewRow In dgv.Rows
If Val(row.Cells(col_name).Value) > max Then
max = Val(row.Cells(col_name).Value)
End If
Next
get_col_max = max
End Function
Function get_col_min(ByVal dgv As DataGridView, ByVal col_name As String) As Double
Dim min As Double = 0
If dgv.Rows.Count > 0 Then min = Val(dgv.Rows(0).Cells(col_name).Value)
For Each row As DataGridViewRow In dgv.Rows
If Val(row.Cells(col_name).Value) < min Then
min = Val(row.Cells(col_name).Value)
End If
Next
get_col_min = min
End Function
Private Sub BtnHitung_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnHitung.Click
Dim a, b As Integer
awal()
Dgv1.copyTo(Dgv2)
For a = 0 To Dgv2.Rows.Count - 1
dr = openDR("SELECT c.nilai FROM tb_rel_alternatif2 r " &
" LEFT JOIN tb_crips2 c ON c.kode_crips = r.kode_crips " &
" WHERE nim='" & Dgv2.Rows(a).Cells(0).Value & "' ORDER BY r.kode_kriteria")
b = 2
While dr.Read
Dgv2.Rows(a).Cells(b).Value = dr(0)
b = b + 1
End While
Next
Dgv2.copyTo(Dgv3)
For Each row As DataGridViewRow In Dgv2.Rows
For b = 2 To Dgv2.Columns.Count - 1
Dim v = row.Cells(b).Value
If Dgv2.Columns(b).ToolTipText = "benefit" Then
Dgv3.Rows(row.Index).Cells(b).Value = v / get_col_max(Dgv2, Dgv2.Columns(b).Name)
Else
Dgv3.Rows(row.Index).Cells(b).Value = get_col_min(Dgv2, Dgv2.Columns(b).Name) / v
End If
Next
Next
dr = openDR("SELECT kode_kriteria, bobot FROM tb_kriteria2 ORDER BY kode_kriteria")
While dr.Read()
Dgv3.Columns(dr(0).ToString()).ToolTipText = dr(1).ToString()
End While
Dgv3.copyTo(Dgv4)
For Each row As DataGridViewRow In Dgv3.Rows
For b = 2 To Dgv3.Columns.Count - 1
Dim v = row.Cells(b).Value
Dgv4.Rows(row.Index).Cells(b).Value = v * Val(Dgv3.Columns(b).ToolTipText)
Next
Next
Dgv4.Columns.Add("total", "Total")
For Each row As DataGridViewRow In Dgv4.Rows
For b = 2 To Dgv2.Columns.Count - 1
row.Cells("total").Value = row.Cells("total").Value + row.Cells(b).Value
Next
Next
Dgv4.copyTo(Dgv5)
Dgv5.Sort(Dgv5.Columns("total"), System.ComponentModel.ListSortDirection.Descending)
For Each row As DataGridViewRow In Dgv5.Rows
execute("UPDATE tb_alternatif2 SET total=#0, rank=#1 WHERE nim=#2", row.Cells("total").Value, row.Index + 1, row.Cells("nim").Value)
Next
TabControl1.SelectedTab = TabRangking
BtnCetak.Enabled = True
End Sub
Private Sub BtnCetak_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnCetak.Click
LapRangking.ShowAsChild(Me.MdiParent)
End Sub
Private Sub BtnKeluar_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnKeluar.Click
Me.Close()
End Sub
End Class

Answer 1

Why are your using dr.Read() at one place and dr.Read in another. Underlined in RED. Maybe the DataReader is not populated yet!, It should be dr.Read()

Answer 2

That error occurs when you try to access an array or other collection with an index that doesn't exist. Note that indexing starts at 0 all the way to Count - 1.
From you screenshot I can see the error occurs at this line Dgv1.Rows(a).Cells(b).Value = dr(0). a is defined in a For loop this way, For a = 0 To Dgv1.Rows.Count - 1 so it is unlikely that is the culprit.
You may want to check the value of b which you have started with a value of 2. If you're trying to access the second item in the collection, you will have to change that line to read...
Dim b As Integer = 1 ' If you wanted to start from the 2nd cell.
While dr.Read
Dgv1.Rows(a).Cells(b).Value = dr(0)
b = b + 1
End While
b is likely growing past the number of cells you have and causing that problem.
Note: I have changed the definition of b to start at 1
Update 2
After looking at your code again, I'm seeing something that I seem to have missed when looking at line that caused the error. You are defining b as, Dim b As Integer = 2 ' I recommended changing that to 1 and using it to access the columns in your dataset/reader. But when I look at your queries, something else reveals itself. The 1st one in the awal() method is
SELECT * FROM tb_alternatif2 ORDER BY nim
which returns an ordered set with an unknown (to me anyway) number of rows and columns. You are then looping through adding the 1st and 2nd columns of the data reader to rows of what I assume is a data grid view. After that, you make a call to another query
SELECT kode_kriteria, atribut FROM tb_kriteria2 ORDER BY kode_kriteria
which returns an ordered set with 2 columns that you add as columns to the data grid view. Next you have the query
SELECT c.nama_crips FROM tb_rel_alternatif2 r --... truncated
which returns one column which is when you are defining b. Somewhere between the number of columns you are creating and then addressing them with b, you are probably hitting an off by one error. Or more than off by one. Assuming the 2nd query creates for you 10 columns and the third query returns 15 rows, you will quickly run out of columns to address using .Cells(b).Value in your code.
It is unclear to me what you are trying to do with this, but I would recommend trying to define your query again and binding once to the data grid. As an aside: I would also recommend using parameters for constructing your queries because the way you have done isn't too secure... SQL injection and all that.