Question

我正在研究这个项目，并被要求编写一个代码来将InvoiceDB和CustomerDB中的数据连接到Form1.Cs。我完成了我的代码但不知何故它没有用。当我运行程序时，form1中的Listview无法从类中获取数据。我想请求专家提供一些帮助。谢谢。

我的代码Form1.cs

    private void Form1_Load(object sender, EventArgs e)
    {
        {
            **//Get data from Invoice and Customer Class**
            List<Invoice> invoiceList = InvoiceDB.GetInvoices();
            List<Customer> customerList = CustomerDB.GetCustomers();

            **//Query expression**
            var invoices = from invoice in invoiceList
                               join customer in customerList
                               on invoice.CustomerID equals customer.CustomerID
                                orderby customer.Name, invoice.InvoiceTotal descending
                           select new {customer.Name, invoice.InvoiceID, invoice.InvoiceDate, invoice.InvoiceTotal};

            **//Executes the query**
           string customerName = " ";
            int i = 0;
            foreach (var invoice in invoices)
            {
                if (invoice.Name != customerName)
                {
                    lvInvoice.Items.Add(invoice.Name);
                    customerName = invoice.Name;
                }
                else
                {
                    lvInvoice.Items.Add(" ");
                }
                lvInvoice.Items[i].SubItems.Add(invoice.InvoiceID.ToString());
                lvInvoice.Items[i].SubItems.Add(Convert.ToDateTime(invoice.InvoiceDate).ToShortDateString());
                lvInvoice.Items[i].SubItems.Add(invoice.InvoiceTotal.ToString("C"));
                i += 1;
            }
    }
    }

CustomerDB Class

public static class CustomerDB
{

    private const string Dir = @""; 
    private const string Path = Dir + "CustomersX23.txt";

    public static List<Customer> GetCustomers()
    {
        List<Customer> customers = new List<Customer>();

        StreamReader textIn = new StreamReader(
            new FileStream(Path, FileMode.Open, FileAccess.Read));

        while (textIn.Peek() != -1)
        {
            string row = textIn.ReadLine();
            string[] columns = row.Split('|');
            Customer customer = new Customer();
            customer.CustomerID = Convert.ToInt32(columns[0]);
            customer.Name = columns[1];
            customers.Add(customer);
        }

        textIn.Close();
        return customers;
    }

InvoiceDB类

public static class InvoiceDB
{

    private const string Dir = @"";
    private const string Path = Dir + "Invoices.txt";

    public static List<Invoice> GetInvoices()
    {
        List<Invoice> invoices = new List<Invoice>();

        StreamReader textIn = new StreamReader(
            new FileStream(Path, FileMode.Open, FileAccess.Read));

        while (textIn.Peek() != -1)
        {
            string row = textIn.ReadLine();
            string[] columns = row.Split('|');
            Invoice invoice = new Invoice();
            invoice.InvoiceID = Convert.ToInt32(columns[0]);
            invoice.CustomerID = Convert.ToInt32(columns[1]);
            invoice.InvoiceDate = Convert.ToDateTime(columns[2]);
            invoice.ProductTotal = Convert.ToDecimal(columns[3]);
            invoice.SalesTax = Convert.ToDecimal(columns[4]);
            invoice.Shipping = Convert.ToDecimal(columns[5]);
            invoice.InvoiceTotal = Convert.ToDecimal(columns[6]);
            invoices.Add(invoice);
        }

        textIn.Close();
        return invoices;
    }

Answer 1

当ListView处于详细模式时，您应该定义ColumnHeaderCollection添加要在ListView中显示的列。如果没有定义ColumnHeaderCollection，ListView将显示为空

MSDN的这句话解释了它

Columns属性返回包含的集合 ListView控件中显示的ColumnHeader对象。 ColumnHeader对象定义显示在的列 View属性设置为Details时的ListView控件。每一栏用于显示ListView中每个项目的子项信息。有关如何操作中的项目的更多信息集合，请参阅ListView.ColumnHeaderCollection。

您应该将列添加到ListView，类似这样

lvInvoice.Columns.Add("Name", -2, HorizontalAlignment.Left);
lvInvoice.Columns.Add("ID", -2, HorizontalAlignment.Left);
lvInvoice.Columns.Add("Date", -2, HorizontalAlignment.Left);
lvInvoice.Columns.Add("Total", -2, HorizontalAlignment.Left);

添加方法有many overloads，选择最适合您的任务

客户发票表格;通用名单; C＃

1 个答案: