[Solved] Input string was not in a correct format in TextBox with VB.Net

Dear Sir,

why Input string was not in a correct format in my textbox with VB.NET?

Is there something wrong with my code?

Please Guide me.

Thanks

Code in Form1

Imports System.ComponentModel
Imports System.Data.OleDb
Imports Dapper

Public Class Form1
    Private bindingSource As BindingSource = Nothing
    Private salesservices As New SalesService()
    Private Sub CalculateTotalValue()
        Dim tot As Double = 0
        For Each item As DataGridViewRow In DataGridView1.Rows
            Dim val As Double
            Dim val2 As Double
            Dim val3 As Double
            Double.TryParse(CType(item.Cells("Qty").Value, String), val)
            Double.TryParse(CType(item.Cells("Price").Value, String), val2)
            Double.TryParse(CType(item.Cells("Discount").Value, String), val3)
            tot += (val * val2) - (val3)
        Next item
        lblValue.Text = tot.ToString("N2")
        'lblChange.Text = (cash - tot).ToString("N2")
    End Sub
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Txtinvono.Text = "1000"
        DataGridView1.AllowUserToAddRows = False
        bindingSource = New BindingSource With {.DataSource = New BindingList(Of Salesdetail)(CType(salesservices.GetSalesdetail(Txtinvono.Text), IList(Of Salesdetail)))}
        DataGridView1.DataSource = bindingSource
        DataGridView1.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells)
        CalculateTotalValue()
    End Sub

    Private Sub BtnPayment_Click(sender As Object, e As EventArgs) Handles BtnPayment.Click
        Using frm = New Payment()
            frm.LblInvono.Text = Me.Txtinvono.Text
            If frm.ShowDialog() = DialogResult.OK Then
            End If
        End Using
    End Sub
End Class
Public Class Sales
    Public Property Invno() As String
    Public Property DateInvno() As Date
    Public Property Totalinv() As Integer
    Public Property DiscountTotal() As Integer
    Public Property Paymentofterm() As String
    Public Property CashPayment() As Integer
    Public Property NCashPayment() As Integer

    Public Property Sales() As New List(Of Salesdetail)()
End Class

Public Class Salesdetail
    Public Property No() As Integer
    Public Property Invno() As String
    Public Property CodeProduct() As String
    Public Property Qty() As Integer
    Public Property Price() As Integer
    Public Property Discount() As Integer
    Public Property Total() As Integer
End Class

Public Class SalesService
    Public Function GetOledbConnectionString() As String
        Return "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Sales.accdb;Persist Security Info=False;"
    End Function
    Private ReadOnly _conn As OleDbConnection
    Private _connectionString As String = GetOledbConnectionString()
    Public Sub New()
        _conn = New OleDbConnection(_connectionString)
    End Sub
    Public Function GetSalesdetail(ByVal Invno As String) As IEnumerable(Of Salesdetail)
        Dim sql = $"SELECT * FROM Salesdetail WHERE Invno = '{Invno}'"
        Using _conn = New OleDbConnection(GetOledbConnectionString())
            Return _conn.Query(Of Salesdetail)(sql).ToList()
        End Using
    End Function
    Public Function GetSales(ByVal Invno As String) As Sales
        Dim sql = $"SELECT * FROM Sales WHERE Invno = '{Invno}'"
        Using _conn = New OleDbConnection(GetOledbConnectionString())
            Return _conn.Query(Of Sales)(sql).FirstOrDefault()
        End Using
    End Function

End Class

Code in Payment

Public Class Payment
    Private salesservices As New SalesService()
    Private Sub Payment_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim sales = salesservices.GetSales(LblInvono.Text)
        LabelTotalvalue.Text = sales.Totalinv.ToString("N0")
        txtDiscount.Text = sales.DiscountTotal.ToString("N0")
        txtPayment.Text = (sales.CashPayment + sales.NCashPayment).ToString("N0")
        LabelChange.Text = ((sales.CashPayment + sales.NCashPayment) - sales.Totalinv).ToString("N0")
    End Sub
    Private Sub OnTextChanged(sender As Object, e As EventArgs) Handles txtPayment.TextChanged, txtDiscount.TextChanged
        Dim payment As Double = 0
        Dim discount As Double = 0
        If Not String.IsNullOrEmpty(txtPayment.Text) OrElse Not String.IsNullOrEmpty(txtDiscount.Text) Then
            payment = Convert.ToDouble(txtPayment.Text)
            discount = Convert.ToDouble(txtDiscount.Text)
            LabelChange.Text = (Convert.ToDouble(LabelTotalvalue.Text) - discount - payment).ToString("N0")
        Else
            LabelChange.Text = "-" & Convert.ToDouble(LabelTotalvalue.Text).ToString("N0")
        End If
    End Sub
    Private Sub OnText_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtPayment.KeyPress, txtDiscount.KeyPress
        If Not Char.IsControl(e.KeyChar) AndAlso Not Char.IsDigit(e.KeyChar) Then
            e.Handled = True
        End If
    End Sub
    Private Sub txtPayment_KeyUp(sender As Object, e As KeyEventArgs) Handles txtPayment.KeyUp
        txtPayment.Text = txtPayment.Text.Replace(",", "")
        Dim discount As Double = 0
        Dim payment As Double = 0
        If Not String.IsNullOrEmpty(txtPayment.Text) Then
            'error in line code below
            payment = Convert.ToDouble(txtPayment.Text)
            LabelChange.Text = (Convert.ToDouble(LabelTotalvalue.Text) - discount - payment).ToString("N0")
            txtPayment.Text = Convert.ToDouble(txtPayment.Text).ToString("N0")
            txtPayment.[Select](txtPayment.Text.Length, 0)
        End If
    End Sub
    Private Sub txtDiscount_KeyUp(sender As Object, e As KeyEventArgs) Handles txtDiscount.KeyUp
        txtDiscount.Text = txtPayment.Text.Replace(",", "")
        Dim discount As Double = 0
        Dim payment As Double = 0
        If Not String.IsNullOrEmpty(txtPayment.Text) Then
            discount = Convert.ToDouble(txtDiscount.Text)
            LabelChange.Text = (Convert.ToDouble(LabelTotalvalue.Text) - discount - payment).ToString("N0")
            txtDiscount.Text = Convert.ToDouble(txtDiscount.Text).ToString("N0")
            txtDiscount.[Select](txtPayment.Text.Length, 0)
        End If
    End Sub
End Class