Question

我正在尝试使用winforms进行预订系统。我有一个组合框，您可以从中选择一到十个数字。我也有10个组合框，我只希望显示的组框数量等于组合框中的选定数字。在组合框中，我有另一个组合框，我可以在其中选择座位编号，这就是为什么重要的是不能同时显示所有框。我有点失落，我曾试图使用动作玩家，但我没有成功。

这里我称之为组合框的GUI：

private void btnMakeBook_Click(object sender, EventArgs e)
    {
        ServiceReferenceBooking.BookingServiceClient bookingService = new ServiceReferenceBooking.BookingServiceClient();
        ServiceReferenceTickets.TicketsServiceClient ticketsService = new ServiceReferenceTickets.TicketsServiceClient();
        splitContainer1.Panel2.Controls.Clear();
        InitializeMakeBookingComponents();

        var allBookings = bookingService.GetAllBookings();
        dataGridView2.DataSource = allBookings;

        cbTickets.ValueMember = "amount";
        cbTickets.DisplayMember = "amount";
        cbTickets.DataSource = ticketsService.GetAllTickets();

    }

这是我想要制作的活动：

private void cbTickets_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (cbTickets.SelectedItem.ToString() == "2")
            {
                gboxSeat2.Visible = true;
            }   
    }

我收到错误：对象引用未设置为对象的实例。它位于if语句所在的行上。

这是我尝试创建的事件，但选择2时GroupBox未显示。

希望你们能帮忙！感谢

Answer 1

SelectedIndex和SelectedItem之间存在差异，第一个是所选项目的基于0的索引，第二个是您要查找的实际项目。试试这个

private void cbTickets_SelectedIndexChanged(object sender, EventArgs e)
{
    if (((ComboBox)sender).SelectedItem == "2")        
    {
        gboxSeat2.Visible = true;
    }
}

充实我的建议：

public partial class Form1 : Form
{
    //Declare your basic controls here
    GroupBox gboxSeat1 = new GroupBox() { BackColor = Color.Red, Visible=false};
    GroupBox gboxSeat2 = new GroupBox() { BackColor = Color.Blue, Visible = false };
    GroupBox gboxSeat3 = new GroupBox() { BackColor = Color.Green, Visible = false };
    GroupBox gboxSeat4 = new GroupBox() { BackColor = Color.Orange, Visible = false };
    ComboBox cbTickets = new ComboBox() { Items = { "0", "1", "2", "3", "4" }, Height = 35, Width = 150 };
    public Form1()
    {
        InitializeComponent();
        //Setup handlers and add them to the panel
        cbTickets.SelectedIndexChanged += comboBox2_SelectedIndexChanged;
        panel1.Controls.Add(gboxSeat1);
        panel1.Controls.Add(gboxSeat2);
        panel1.Controls.Add(gboxSeat3);
        panel1.Controls.Add(gboxSeat4);
        panel1.Controls.Add(cbTickets);

    }

    private void InitializeBookingComponents()
    {
        //Arrange your controls the way you want here
    }

    private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (((ComboBox)sender).SelectedItem == "2")
            gboxSeat2.Visible = true;
    }

}

这将确保您只有一个控件，您可以在闲暇时将其移除或添加到面板中，只保留一个控件

Winform Combobox使用值更改GUI

1 个答案: