Trung tâm cá nhân
sách gpt4 ăn đã đi

C# - nhân viên nền?

In lại 作者：太空狗 更新时间：2023-10-30 01:09:19 30 4
mua khóa gpt4 giày nike

我有一个相当复杂的程序，所以我不会在这里转储整个程序。这是一个简化版本:

class Report {
    private BackgroundWorker worker;

    public Report(BackgroundWorker bgWorker, /* other variables, etc */) {
        // other initializations, etc
        worker = bgWorker;
    }

    private void SomeCalculations() {
        // In this function, I'm doing things which may cause fatal errors.
        // Example: I'm connecting to a database. If the connection fails, 
        // I need to quit and have my background worker report the error
    }
}


// In the GUI WinForm app:
// using statements, etc.
using Report;

namespace ReportingService {
    public partial class ReportingService : Form {

        // My background worker
        BackgroundWorker theWorker = new BackgroundWorker() {
            WorkerReportsProgress = true
        };

        // The progress changed event
        void worker_ProgressChanged(object sender, ProgressChangedEventArgs e) {
            // e.UserState and e.ProgressPercentage on some labels, etc.
        }

        // The do work event for the worker, runs the number crunching algorithms in SomeCalculations();
        void worker_DoWork(object sender, DoWorkEventArgs e) {
            Report aReport = e.Argument as Report;

            aReport.SomeCalculations();
        }

        // The completed event, where all my trouble is. I don't know how to retrieve the error,
        // or where it originates from.
        void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
            // How, exactly, do I get this error message? Who provides it? How?
            if (e.Error != null) {
                MessageBox.Show("Error: " + (e.Error as Exception).ToString());
            }
            else if (e.Cancelled) {
                MessageBox.Show("Canceled");
            }
            // operation succeeded
            khác {
                MessageBox.Show("Success");
            }
        }

        // Initialization of the forml, etc
        public ReportingService() {
            InitializeComponent();

            theWorker.ProgressChanged += worker_ProgressChanged;
            theWorker.DoWork += worker_DoWork;
            theWorker.RunWorkerCompleted += worker_RunWorkerCompleted;
        }

        // A button that the user clicks to execute the number crunching algorithm
        private void sumButton_Click(object sender, EventArgs e) {
            Report myReport = new Report(theWorker, /* some other variables, etc */)
            theWorker.RunWorkerAsync(myReport);
        }
    }
}

这是我的逻辑，如果我以错误的方式进行此操作，请纠正我:

  1. 我从 GUI 中抽象出该类，因为它大约有 2000 行，并且需要成为它自己的自包含对象。

  2. 我将后台工作人员传递到我的类(class)，以便我可以报告我的数字处理进度。

我不知道如何做的是让后台工作人员知道我的类(class)内部发生了错误。为了获得 RunWorkerCompleted 参数作为异常，我的 try/catch block 需要去哪里，我应该在 catch block 中做什么？

感谢您的帮助!

biên tập:

我尝试了以下方法来测试错误处理:

请记住，我损坏了我的数据库连接字符串是为了故意接收一条错误消息。

在我的类里面我这样做:

// My number crunching algorithm contained within my class calls a function which does this:

// try {
    using (SqlConnection c = GetConnection()) { // note: I've corrupted the connection string on purpose
        c.Open(); // I get the exception thrown here
        using (SqlCommand queryCommand = new SqlCommand(query, c)) { /* Loop over query, etc. */ }
        c.Close();  
    }
// } catch (Exception e) { }

1.根据我的理解，未处理的异常被转换为 RunWorkerCompletedEventArgs của Lỗi 部分？当我尝试这个时，我得到以下信息:

// In my winform application I initialize my background worker with these events:

void gapBW_DoWork(object sender, DoWorkEventArgs e) {
    Report aReport = e.Argument as Report;
    Report.Initialize(); // takes ~1 minute, throws SQL exception
    Report.GenerateData(); // takes around ~2 minutes, throws file IO exceptions
}

void gapBW_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {   
    if (e.Error != null) { // I can't get this to trigger, How does this error get set?
        MessageBox.Show("Error: " + (e.Error as Exception).ToString());
    }
    else if (e.Cancelled) {
        MessageBox.Show("Canceled: " + (e.Result).ToString());
    }
    khác {
        MessageBox.Show("Success");
    }
}

Visual Studio 说我的应用程序因未处理的异常而因 c.Open() 而阻塞。

2。当我在我的 DoWork 函数中放置一个 try/catch block 时:

void gapBW_DoWork(object sender, DoWorkEventArgs e) {
    thử {
        Report aReport = e.Argument as Report;
        aReport.Initialize(); // throws SQL exceptions
        aReport.GenerateData(); // throws IO file exceptions
    }
    catch (Exception except) {
        e.Cancel = true;    
        e.Result = except.Message.ToString();
    }
}

void gapBW_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {   
    if (e.Error != null) { // I can't get this to trigger, How does this error get set?
        MessageBox.Show("Error: " + (e.Error as Exception).ToString());
    }
    else if (e.Cancelled) {
        MessageBox.Show("Canceled: " + (e.Result).ToString());
    }
    khác {
        MessageBox.Show("Success");
    }
}

我在自动生成的 Application.Run(new ReportingService()); 行的 Program.cs 中收到 TargetInvocationException was unhandled。我在 RunWorkerCompleted 上放置了一个断点，可以看到 e.Cancelled = true、e.Error = null 和 e.UserState = null。 e.Cancelled 中包含的消息只是“操作已被取消”。我想我正在从 e.Result 的无效转换中接收到 TargetInvocationException(因为它为 null)。不过，我想知道的是，为什么 e.Error 仍然为 null 而 e.Canceled 不包含有关Tại sao操作被取消的任何有用信息？

3。当我尝试在异常捕获时从 DoWork 中设置 e.Canceled = true; 时，我设法触发了我的 TRONG else if (e.Cancelled) { 行>RunWorkerCompleted 函数。我以为这是为请求取消作业的用户保留的？我是否从根本上误解了后台工作人员的工作方式？

câu trả lời hay nhất

我尝试了这个小测试程序，它按预期工作:

void tĩnh Main(chuỗi[] args)
{
    var worker = new BackgroundWorker();

    worker.DoWork += (sender, e) => { throw new ArgumentException(); };
    worker.RunWorkerCompleted += (sender, e) => Console.WriteLine(e.Error.Message);
    worker.RunWorkerAsync();

    Console.ReadKey();
}

但是当我在调试器中运行该程序时，我还在 throw 语句中收到了有关未处理异常的消息。但我只是再次按下 F5，它继续没有任何问题。

关于C# - 后台 worker ？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7115058/

30 4 0
Đề xuất bài viết: c# - DataGridView 自定义排序
Đề xuất bài viết: c# - 采用 List[] 的 Action 委托(delegate)的问题
Đề xuất bài viết: c# - WPF 向后查看 ListView
Đề xuất bài viết: c# - 数组比较作为 C# 中的字典键
太空狗
Hồ sơ

Tôi là một lập trình viên xuất sắc, rất giỏi!

Nhận phiếu giảm giá taxi Didi miễn phí
Phiếu giảm giá taxi Didi
Các bài viết phổ biến trên toàn bộ trang web
Chứng chỉ ICP Bắc Kinh số 000000
Hợp tác quảng cáo: 1813099741@qq.com 6ren.com
Xem sitemap của VNExpress