asynccalcpiform.cs

中文名：Windows Forms 程序设计 英文名：Windows Forms Programming in c# 作者： Chris Sells 翻译： 荣耀 蒋贤哲 出版社：人民

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Text;
using System.Threading;
using System.Windows.Forms;

namespace MySecondApp {

  public partial class AsyncCalcPiForm : Form {

    public AsyncCalcPiForm() {
      InitializeComponent();
    }

    private void calcButton_Click(object sender, EventArgs e) {

      // Set UI state
      this.calcButton.Enabled = false;
      int digits = (int)this.decimalPlacesNumericUpDown.Value;
      this.resultsTextBox.Text = "";
      this.calcToolStripStatusLabel.Text = "Calculating...";
      this.calcToolStripProgressBar.Visible = true;

      // Initiate asynchronous worker thread
      this.backgroundWorker.RunWorkerAsync(digits);
    }

    private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) {
      // This method will run on a thread other than the UI thread.
      // Be sure not to manipulate any Windows Forms controls created
      // on the UI thread from this method.

      // Get number of digits to calculate pi to
      int digits = int.Parse(e.Argument.ToString());

      StringBuilder pi = new StringBuilder("3", digits + 2);

      // Get the BackgroundWorker that raised this event.
      BackgroundWorker worker = sender as BackgroundWorker;

      // Report initial progress
      worker.ReportProgress(0, pi.ToString());

      // Calculate rest of pi, if required
      if( digits > 0 ) {
        pi.Append(".");

        for( int i = 0; i < digits; i += 9 ) {

          // Calculate next i decimal places
          int nineDigits = NineDigitsOfPi.StartingAt(i + 1);
          int digitCount = Math.Min(digits - i, 9);
          string ds = string.Format("{0:D9}", nineDigits);
          pi.Append(ds.Substring(0, digitCount));

          // Report current progress
          int digitsSoFar = i + digitCount;
          float progressPercentage = (float)digitsSoFar / (float)digits * 100;
          worker.ReportProgress((int)progressPercentage, pi.ToString());
        }
      }
    }

    private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) {
      // Executing on the UI thread
      string pi = (string)e.UserState;
      this.calcToolStripProgressBar.Value = e.ProgressPercentage;
      this.resultsTextBox.Text = pi;
    }

    private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
      // Reset progress status strip
      this.calcButton.Enabled = true;
      this.calcToolStripStatusLabel.Text = "Ready";
      this.calcToolStripProgressBar.Visible = false;
    }
  }
}