fill: SelectCommand connection property has not been initialized - vb.net

Question

Dim SiparisOnayi As String
Dim SiparisDurumu As String
Dim SiparisIli As String
Dim SiparisOdemeYontemi As String
Dim SiparisKargoFirmasi As String
Dim SiparisSatisKanali As String
Dim a1, a2, a3, a4, a5, a6, a7, soncom As String
If ComboBox1.Text = Nothing Then
a1 = Nothing
Else
SiparisOnayi = ComboBox1.Text
a1 = " and Siparis_Onay = SiparisOnayi"
End If
If ComboBox2.Text = Nothing Then
a2 = Nothing
Else
SiparisDurumu = ComboBox2.Text
a2 = " and Siparis_Durumu = SiparisDurumu "
End If
If ComboBox3.Text = Nothing Then
a3 = Nothing
Else
SiparisIli = ComboBox3.Text
a3 = " and Musteri_IL = SiparisIli "
End If
If ComboBox4.Text = Nothing Then
a4 = Nothing
Else
a4 = " and Kullanici_Kodu = SiparisKullanicisi"
End If
If ComboBox5.Text = Nothing Then
a5 = Nothing
Else
SiparisOdemeYontemi = ComboBox5.Text
a5 = " and Odeme_Yontemi = SiparisOdemeYontemi"
End If
If ComboBox6.Text = Nothing Then
a6 = Nothing
Else
SiparisKargoFirmasi = ComboBox6.Text
a6 = " and Kargo_Adi = SiparisKargoFirmasi"
End If
If ComboBox7.Text = Nothing Then
a7 = Nothing
Else
SiparisSatisKanali = ComboBox7.Text
a7 = " and Satis_Kanali = SiparisSatisKanali"
End If
soncom = "SELECT * FROM `Siparisler` WHERE `Siparis_Tarihi` BETWEEN #d1 and #d2" & a1 & a2 & a3 & a4 & a5 & a6 & a7 & ", connection"
Try
Dim command As New MySqlCommand(soncom)
command.Parameters.Add("#d1", MySqlDbType.DateTime).Value = DateTimePicker2.Value
command.Parameters.Add("#d2", MySqlDbType.DateTime).Value = DateTimePicker3.Value
Dim table As New DataTable
Dim adapter As New MySqlDataAdapter(command)
adapter.Fill(table)
DataGridView1.DataSource = table
Label12.Text = "Toplam " & table.Rows.Count & " Kayıt bulundu ve gösteriliyor."
myconnection.close()
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
Error : fill: SelectCommand connection property has not been initialized
How can I fix my code?

Answer 1

The & ", connection" at the end of this line looks wrong to me:
soncom = "SELECT ..." & a1 & ... a7 & ", connection"
But also, you need a connection object in addition to a command and an adapter, the way the WHERE clause is currently assembled would be extremely vulnerable to sql injection issues if it worked at all, but it won't because the combobox values are never actually interpolated into the final string, and the code is vulnerable to leaving the connection hanging open if an exception is thrown during the call to Fill().
This should fix all of those issues (once you fill in the connection string):
Dim table As New DataTable
Using connection As New MySqlConnection("connection string here")
Using command As New MySqlCommand("", connection)
Using adapter As New MySqlDataAdapter(command)
Dim sql As String = "SELECT * FROM `Siparisler` WHERE `Siparis_Tarihi` BETWEEN #d1 and #d2"
If Not string.IsNullOrWhitespace(ComboBox1.Text) Then
sql += " and Siparis_Onay = #SiparisOnayi"
command.Parameters.AddWithValue("#SiparisOnayi", ComboBox1.Text)
End if
If Not string.IsNullOrWhitespace(ComboBox2.Text) Then
sql += " and Siparis_Durumu = #SiparisDurumu"
command.Parameters.AddWithValue("#SiparisDurumu", ComboBox2.Text)
End If
If Not string.IsNullOrWhitespace(ComboBox3.Text) Then
sql += " and Musteri_IL = #SiparisIli"
command.Parameters.AddWithValue("#SiparisIli", ComboBox3.Text)
End If
If Not string.IsNullOrWhitespace(ComboBox4.Text) Then
sql +" and Kullanici_Kodu = #SiparisKullanicisi"
command.Parameters.AddWithValue("#SiparisKullanicisi", ComboBox4.Text)
End If
If Not string.IsNullOrWhitespace(ComboBox5.Text) Then
sql += " and Odeme_Yontemi = #SiparisOdemeYontemi"
command.Parameters.AddWithValue("#SiparisOdemeYontemi", ComboBox5.Text)
End If
If Not string.IsNullOrWhitespace(ComboBox6.Text) Then
sql += " and Kargo_Adi = #SiparisKargoFirmasi"
command.Parameters.AddWithValue("#SiparisKargoFirmasi", ComboBox6.Text)
End If
If Not string.IsNullOrWhitespace(ComboBox7.Text) Then
sql += " and Satis_Kanali = #SiparisSatisKanali"
command.Parameters.AddWithValue("#SiparisSatisKanali", ComboBox7.Text)
End If
command.CommandText = sql
command.Parameters.Add("#d1", MySqlDbType.DateTime).Value = DateTimePicker2.Value
command.Parameters.Add("#d2", MySqlDbType.DateTime).Value = DateTimePicker3.Value
Try
adapter.Fill(table)
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Using
End Using
End Using
DataGridView1.DataSource = table
Label12.Text = $"Toplam {table.Rows.Count} Kayıt bulundu ve gösteriliyor."