Question

我需要帮助来解决我的代码问题。我有3节课。 Class 1是一个带有Progressbar的WinForm。第2类是事件被触发的地方。第3类是进度的EventArg。该程序编译出任何错误，但当我单击按钮时，进度条不会移动！

namespace WindowsFormsApplication1
{

class Class1
{
    //Declaring a delegate
    public delegate void StatusUpdateHandler(object sender, ProgressEventArgs e);

    //Declaraing an event
    public event StatusUpdateHandler OnUpdateStatus;

    public int recno;

    public void Func()
    {
        //time consuming code
        for (recno = 0; recno <= 100; recno++)
        {
            UpdateStatus(recno);
        }

    }

    public void UpdateStatus(int recno)
   {    
        // Make sure someone is listening to event         
        if (OnUpdateStatus == null) return;          <--------------OnUpdateStatus   is     always null not sure why?
        ProgressEventArgs args = new ProgressEventArgs(recno);         
        OnUpdateStatus(this, args);     
    } 
}
}


namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{

    private Class1 testClass;

    public Form1()
    {
        InitializeComponent();

        testClass = new Class1();
        testClass.OnUpdateStatus += new Class1.StatusUpdateHandler(UpdateStatus);
    }


    public void button1_Click(object sender, EventArgs e)
    {

        Class1 c = new Class1();
        c.Func();

    }


    public void UpdateStatus(object sender, ProgressEventArgs e)

    {
        progressBar1.Minimum = 0;
        progressBar1.Maximum = 100;
        progressBar1.Value = e.Recno;

    }
}
}



namespace WindowsFormsApplication1
{
public class ProgressEventArgs : EventArgs
{

    public  int Recno { get; private set; }

    public ProgressEventArgs(int recno)
    {
        Recno = recno;
    }

}
}

Answer 1

您从未向c的事件添加事件处理程序。

您确实为testClass'事件添加了处理程序，但从未使用testClass。

Answer 2

您正在使用Class1的两个不同对象。

在按钮单击处理程序中，对象c与成员对象testClass不同。使用testClass代替c，它可以解决问题

public void button1_Click(object sender, EventArgs e)
{
    testClass.Func();
}

c＃Progress Bar基于事件和委托不起作用

2 个答案: