How to save integer and decimal datatype from datagridview to database ms access in VB.NET [duplicate] - vb.net

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I have been searching for a solution for my code error, which says that there is a data mismatch to my database declared datatype. I am saving my data grid view's data into ms access database but it show an error of data mismatch for saving PRICE and QUANTITY data.
I have tried adding parameters and it shows the error System.NullReferenceException: 'Object reference not set to an instance of an object.'
'After comfirm only save in database
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
If (MessageBox.Show("Comfrim the orders?", "Comfirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = DialogResult.Yes) Then
If OrderDataGridView.Rows.Count > 0 Then
DBConnect = New OleDbConnection
DBConnect.ConnectionString = "Provider=Microsoft.jet.oledb.4.0;data source = ViewOrder.mdb"
For i As Integer = OrderDataGridView.Rows.Count - 1 To 0 Step -1
Dim Query As String
Query = "INSERT INTO ViewOrder.Order (Serve,Table_No, Item_Code, Item_Name, Quantity, Price, Remarks)
VALUES (#Serve, #Table_No, #Item_Code, Item_Name, #Quantity, #Price, #Remarks)"
Dim cmd As New OleDb.OleDbCommand(Query, DBConnect)
cmd.Parameters.Add("#Serve", OleDbType.VarChar).Value = Label8.Text
cmd.Parameters.Add("#Table_No", OleDbType.VarChar).Value = Label10.Text
cmd.Parameters.Add("#Item_Code", OleDbType.VarChar).Value = OrderDataGridView.Rows(i).Cells(0).Value
cmd.Parameters.Add("#Item_Name", OleDbType.VarChar).Value = OrderDataGridView.Rows(i).Cells(1).Value
cmd.Parameters.Add("#Quantity", OleDbType.Integer).Value = OrderDataGridView.Rows(i).Cells(2).Value
cmd.Parameters.Add("#Price", OleDbType.Decimal).Value = OrderDataGridView.Rows(i).Cells(3).Value
cmd.Parameters.Add("#Remarks", OleDbType.VarChar).Value = OrderDataGridView.Rows(i).Cells(4).Value
DBConnect.Open()
Dim Reader As OleDbDataReader
Reader = command.ExecuteReader
DBConnect.Close()
Next
End If
End If
End Sub
But it still show the error.
This is my current code with the error of data mismatch.
Dim Query As String
Query = "INSERT INTO ViewOrder.Order (Serve,Table_No, Item_Code, Item_Name, Quantity, Price, Remarks) VALUES ('" & Label8.Text & "','" & Label10.Text & "','" & OrderDataGridView.Rows(i).Cells(0).Value & "', '" & OrderDataGridView.Rows(i).Cells(1).Value & "','" & OrderDataGridView.Rows(i).Cells(2).Value & "','" & OrderDataGridView.Rows(i).Cells(3).Value & "','" & OrderDataGridView.Rows(i).Cells(4).Value & "')"
Dim Reader As OleDbDataReader
command = New OleDbCommand(Query, DBConnect)
Reader = command.ExecuteReader
DBConnect.Close()
I just need to save the data in database.

Answer 1

From the MS Docs
the order in which OleDbParameter objects are added to the
OleDbParameterCollection must directly correspond to the position of
the question mark placeholder for the parameter in the command text.
Instead of question marks, I like to use parameter names. It is easier to see if I have the order correct. We add the parameters outside the loop because each iteration uses the same parameters. We don't want to keep adding them. Only the values change but not for Serve and TableNo which stay the same for all the Inserts.
Pass the connection string directly to the constructor of the connection.
The Using...End Using blocks ensure that your database objects are closed and disposed even if there is an error.
You do not want a reader for an Insert. A reader is for returned records. You need .ExecuteNonQuery.
You need to check the datatypes of the fields because I just guessed.
The DataGridView.Rows.Count is -2 because subtract one for counting starting at one and collections starting at zero. And subtract another one for the empty row at the bottom of the grid that is included in the count.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Query As String = "INSERT INTO ViewOrder.Order (Serve,Table_No, Item_Code, Item_Name, Quantity, Price, Remarks)
Values(#Serve, #TableNo, #ItemCode,#ItemName, #Quantity, #Price, #Remarks);"
Using DBConnect = New OleDbConnection("Provider=Microsoft.jet.oledb.4.0;data source = ViewOrder.mdb")
Using cmd As New OleDbCommand(Query, DBConnect)
cmd.Parameters.Add("#Serve", OleDbType.VarChar).Value = Label8.Text
cmd.Parameters.Add("#TableNo", OleDbType.VarChar).Value = Label10.Text
cmd.Parameters.Add("#ItemCode", OleDbType.VarChar)
cmd.Parameters.Add("#ItemName", OleDbType.VarChar)
cmd.Parameters.Add("#Quantity", OleDbType.Integer)
cmd.Parameters.Add("#Price", OleDbType.Decimal)
cmd.Parameters.Add("#Remarks", OleDbType.VarChar)
DBConnect.Open()
For i As Integer = 0 To DataGridView1.Rows.Count - 2
cmd.Parameters("#ItemCode").Value = OrderDataGridView.Rows(i).Cells(0).Value
cmd.Parameters("#ItemName").Value = OrderDataGridView.Rows(i).Cells(1).Value
cmd.Parameters("#Quantity").Value = CInt(OrderDataGridView.Rows(i).Cells(2).Value)
cmd.Parameters("#Price").Value = CDec(OrderDataGridView.Rows(i).Cells(3).Value)
cmd.Parameters("#Remarks").Value = OrderDataGridView.Rows(i).Cells(4).Value
cmd.ExecuteNonQuery()
Next
End Using
End Using
End Sub