VB进销存源码究竟包含哪些关键功能？

Imports System.Data.SqlClient
Public Class Form1
    Dim connectionString As String = "Data Source=(local);Initial Catalog=InventoryDB;Integrated Security=True"
    Dim connection As New SqlConnection(connectionString)
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        LoadProducts()
    End Sub
    Private Sub LoadProducts()
        Dim command As New SqlCommand("SELECT * FROM Products", connection)
        Dim adapter As New SqlDataAdapter(command)
        Dim table As New DataTable()
        adapter.Fill(table)
        DataGridView1.DataSource = table
    End Sub
    Private Sub btnAddProduct_Click(sender As Object, e As EventArgs) Handles btnAddProduct.Click
        Dim productName As String = txtProductName.Text
        Dim quantity As Integer = Integer.Parse(txtQuantity.Text)
        Dim price As Decimal = Decimal.Parse(txtPrice.Text)
        Dim command As New SqlCommand("INSERT INTO Products (ProductName, Quantity, Price) VALUES (@ProductName, @Quantity, @Price)", connection)
        command.Parameters.AddWithValue("@ProductName", productName)
        command.Parameters.AddWithValue("@Quantity", quantity)
        command.Parameters.AddWithValue("@Price", price)
        connection.Open()
        command.ExecuteNonQuery()
        connection.Close()
        LoadProducts()
    End Sub
    Private Sub btnSellProduct_Click(sender As Object, e As EventArgs) Handles btnSellProduct.Click
        Dim productName As String = txtProductNameToSell.Text
        Dim quantityToSell As Integer = Integer.Parse(txtQuantityToSell.Text)
        Dim command As New SqlCommand("UPDATE Products SET Quantity = Quantity  @QuantityToSell WHERE ProductName = @ProductName", connection)
        command.Parameters.AddWithValue("@ProductName", productName)
        command.Parameters.AddWithValue("@QuantityToSell", quantityToSell)
        connection.Open()
        command.ExecuteNonQuery()
        connection.Close()
        LoadProducts()
    End Sub
End Class

在这个示例中，我们使用了SQL Server数据库来存储产品信息，我们需要创建一个名为InventoryDB的数据库，并在其中创建一个名为Products的表，包含以下字段：ProductID（自动递增的主键）、ProductName（产品名称）、Quantity（库存数量）和Price（价格）。