在DataGridView的现有项目中添加数量的问题-vb.net

我正在创建一个购物系统，作为我的大学迷你项目，用户可以在其中输入他们想要的商品的条形码，输入的商品将被添加到右侧的网格中，并且作为新的商品添加到左侧的网格中。每个项目都有唯一的条形码，并且可以具有相同的产品代码。当用户输入具有相同产品代码的商品时，数量将添加到左侧的网格中。我遇到一个问题，当需要添加第二个项目数量时，系统会将其检测为新项目，而不是添加数量

例如：产品和物品示例

    Public Sub addRecordTo2ndDGV()
    Try
        dbconnection()
        sql = "SELECT * FROM items_database WHERE Item_Barcode = @ItemBarcode;"
        cmd = New MySqlCommand
        With cmd
            .Connection = conn
            .CommandText = sql
            .Parameters.Clear()
            .Parameters.AddWithValue("@ItemBarcode", formUser.barcodeTB.Text)
        End With
        da = New MySqlDataAdapter
        dt = New DataTable
        da.SelectCommand = cmd
        da.Fill(dt)
        If dt.Rows.Count > 0 Then
            Dim ItemProductCode, ItemBarcode As String
            Dim repeated As Boolean = False
            ItemProductCode = dt.Rows(0).Item(1)
            ItemBarcode = dt.Rows(0).Item(2)
            formUser.itemproductcodeTB.Text = ItemProductCode
            formUser.itembarcodetb.Text = ItemBarcode
            
            For Each row2 As DataGridViewRow In formUser.ItemBarcodeDGV.Rows
                If Convert.ToString(row2.Cells(1).Value) = formUser.itembarcodetb.Text AndAlso Convert.ToString(row2.Cells(0).Value) = formUser.itemproductcodeTB.Text Then
                    MsgBox("QUANTITY WILL MINUS")
                    minusQuantity()
                    formUser.ItemBarcodeDGV.Rows.Remove(row2)
                    MsgBox("QUANTITY HAS MINUS")
                    Exit For

                ElseIf Convert.ToString(row2.Cells(1).Value) <> formUser.itembarcodetb.Text AndAlso Convert.ToString(row2.Cells(0).Value) = formUser.itemproductcodeTB.Text Then
                    MsgBox("QUANTITY WILL ADD")
                    formUser.ItemBarcodeDGV.Rows.Add(New String() {formUser.itemproductcodeTB.Text, formUser.itembarcodetb.Text})
                    addQuantity()
                    MsgBox("QUANTITY HAS ADDED")
                    Exit For

                ElseIf Convert.ToString(row2.Cells(1).Value) <> formUser.itembarcodetb.Text AndAlso Convert.ToString(row2.Cells(0).Value) <> formUser.itemproductcodeTB.Text Then
                    MsgBox("NEW ITEM")
                    formUser.ItemBarcodeDGV.Rows.Add(New String() {formUser.itemproductcodeTB.Text, formUser.itembarcodetb.Text})
                    addRecord()
                    MsgBox("REGISTERED SUCCESSFULL")
                    Exit For
                End If
                Exit For
            Next
        Else
            MsgBox("Barcode not registered!")
            formUser.barcodeTB.Text = ""
            formUser.barcodeTB.Focus()
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        conn.Close()
        da.Dispose()
        formUser.barcodeTB.Text = ""
        clearUserForm()
        retrieveSubTotal()
    End Try
End Sub

Public Sub addRecord()
    If formUser.itemproductcodeTB.Text = "" Then
        MsgBox("Scan a barcode")
    Else
        Try
            dbconnection()
            sql = "SELECT * FROM products_database WHERE Product_Code = @ProductCode;"
            cmd = New MySqlCommand
            With cmd
                .Connection = conn
                .CommandText = sql
                .Parameters.Clear()
                .Parameters.AddWithValue("@ProductCode", formUser.itemproductcodeTB.Text)
            End With
            da = New MySqlDataAdapter
            dt = New DataTable
            da.SelectCommand = cmd
            da.Fill(dt)
            If dt.Rows.Count > 0 Then
                Dim productcode, itemdescription, unitprice As String
                Dim repeated As Boolean = False
                productcode = dt.Rows(0).Item(1)
                itemdescription = dt.Rows(0).Item(3)
                unitprice = dt.Rows(0).Item(4)
                formUser.productcodeTB.Text = productcode
                formUser.itemdescriptionTB.Text = itemdescription
                formUser.unitpriceTB.Text = unitprice
                formUser.unitQuantityTB.Text = "1"

                For Each row As DataGridViewRow In formUser.ProductAddToCartDGV.Rows
                    If Convert.ToString(row.Cells(0).Value) = formUser.productcodeTB.Text AndAlso Convert.ToString(row.Cells(2).Value) = formUser.unitpriceTB.Text Then
                        row.Cells(4).Value = Convert.ToString(row.Cells(3).Value * row.Cells(2).Value)
                    End If
                Next
                formUser.ProductAddToCartDGV.Rows.Add(New String() {formUser.productcodeTB.Text, formUser.itemdescriptionTB.Text, formUser.unitpriceTB.Text, formUser.unitQuantityTB.Text, formUser.unitpriceTB.Text})
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            conn.Close()
            da.Dispose()
        End Try
    End If
End Sub

Public Sub addQuantity()
    If formUser.itemproductcodeTB.Text = "" Then
        MsgBox("Scan a barcode")
    Else
        Try
            dbconnection()
            sql = "SELECT * FROM products_database WHERE Product_Code = @ProductCode;"
            cmd = New MySqlCommand
            With cmd
                .Connection = conn
                .CommandText = sql
                .Parameters.Clear()
                .Parameters.AddWithValue("@ProductCode", formUser.itemproductcodeTB.Text)
            End With
            da = New MySqlDataAdapter
            dt = New DataTable
            da.SelectCommand = cmd
            da.Fill(dt)
            If dt.Rows.Count > 0 Then
                Dim productcode, itemdescription, unitprice As String
                Dim repeated As Boolean = False
                productcode = dt.Rows(0).Item(1)
                itemdescription = dt.Rows(0).Item(3)
                unitprice = dt.Rows(0).Item(4)

                formUser.productcodeTB.Text = productcode
                formUser.itemdescriptionTB.Text = itemdescription
                formUser.unitpriceTB.Text = unitprice
                formUser.unitQuantityTB.Text = "1"

                For Each row As DataGridViewRow In formUser.ProductAddToCartDGV.Rows
                    If Convert.ToString(row.Cells(0).Value) = formUser.productcodeTB.Text AndAlso Convert.ToString(row.Cells(2).Value) = formUser.unitpriceTB.Text Then
                        row.Cells(3).Value = Convert.ToString(Convert.ToInt16(row.Cells(3).Value + 1))
                        row.Cells(4).Value = Convert.ToString(row.Cells(3).Value * row.Cells(2).Value)
                    End If
                Next
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            conn.Close()
            da.Dispose()
        End Try
    End If
End Sub

Public Sub minusQuantity()
    If formUser.itemproductcodeTB.Text = "" Then
        MsgBox("Scan a barcode")
    Else
        Try
            dbconnection()
            sql = "SELECT * FROM products_database WHERE Product_Code = @ProductCode;"
            cmd = New MySqlCommand
            With cmd
                .Connection = conn
                .CommandText = sql
                .Parameters.Clear()
                .Parameters.AddWithValue("@ProductCode", formUser.itemproductcodeTB.Text)
            End With
            da = New MySqlDataAdapter
            dt = New DataTable
            da.SelectCommand = cmd
            da.Fill(dt)
            If dt.Rows.Count > 0 Then
                Dim productcode, itemdescription, unitprice As String
                Dim repeated As Boolean = False
                productcode = dt.Rows(0).Item(1)
                itemdescription = dt.Rows(0).Item(3)
                unitprice = dt.Rows(0).Item(4)

                formUser.productcodeTB.Text = productcode
                formUser.itemdescriptionTB.Text = itemdescription
                formUser.unitpriceTB.Text = unitprice
                formUser.unitQuantityTB.Text = "1"

                For Each row As DataGridViewRow In formUser.ProductAddToCartDGV.Rows
                    If Convert.ToString(row.Cells(0).Value) = formUser.productcodeTB.Text AndAlso Convert.ToString(row.Cells(2).Value) = formUser.unitpriceTB.Text Then
                        row.Cells(3).Value = Convert.ToString(Convert.ToInt16(row.Cells(3).Value - 1))
                        row.Cells(4).Value = Convert.ToString(row.Cells(3).Value * row.Cells(2).Value)
                    End If
                Next
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            conn.Close()
            da.Dispose()
        End Try
    End If
End Sub

这是输出图像