小编Red*_*daa的帖子

我有一个wpf应用程序,我需要显示一个消息框,问题是消息框显示0.5秒,甚至不等待用户单击确定.

MainWindow.xaml.cs:

public partial class MainWindow : Window
{
    public MainWindow()
    {

        //verifying application setting file to see if the connection is ok
        string pathToApp = System.AppDomain.CurrentDomain.BaseDirectory + "settings.sts";
        ApplicationSettings applicationSettings = new ApplicationSettings();
        applicationSettings.ServerIp = "127.0.0.1";
        applicationSettings.ServerDatabase = "test";
        applicationSettings.ServerUserName = "root";
        applicationSettings.MakeConnectionString();
        foreach (char  c in "")
        {
            applicationSettings.ServerPassword.AppendChar(c);
        }



        MySqlConnection connection = new MySqlConnection(applicationSettings.ConnectionString);
        try
        {
            connection.Open();
        }
        catch (Exception e)
        {
            // here the message box shows for 0.5 second and closes immediately
            MessageBox.Show(e.Message);
        }
        finally …

在具有Orders,Customers表的数据库中,我需要将这两个表之间的关系设置为零或一对多关系,这仅仅是因为在我的应用程序中,订单可以存在而无需分配给客户.

我想到的第一个想法是使外键可以为空,这样在创建命令时外键可以为null,但我不知道如何这样做.我正在研究一个模型,所以我可以将它呈现给我的"老师",所以我需要知道如何使用EER图表来完成它.

提前致谢.