C# 下载网络资源的实例

本文主要是介绍C# 下载网络资源的实例，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

这是个通过http下载网络URL所指向的资源的实例，写的比较简陋，还请见谅。

主要用到的控件：SaveFileDialog,ProcessBar等。

主要用到了输入输出流的知识以及多线程的知识。

（关于“如何：对 Windows 窗体控件进行线程安全调用”的问题，欢迎访问http://msdn.microsoft.com/query/dev11.query?appId=Dev11IDEF1&l=ZH-CN&k=k(EHInvalidOperation.WinForms.IllegalCrossThreadCall);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.0);k(DevLang-csharp)&rd=true）

我这里使用了“CheckForIllegalCrossThreadCalls = false;”的方法（等于完全忽视了线程安全~不过省事啊~）

代码很简单，直接贴下来就好了：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace ReadStream
{public partial class Download : Form{public Download(){InitializeComponent();//多线程省些事CheckForIllegalCrossThreadCalls = false;}private int processCount=0;private void button1_Click(object sender, EventArgs e){string urlStr = textBox1.Text;string saveNameStr = textBox2.Text;if (textBox1.Text.Equals("") || textBox2.Text.Equals("")){MessageBox.Show("请填写输入信息");}else{new Thread(new ThreadStart(OnDownLoad)).Start();}}public void OnDownLoad(){button1.Text = "下载中";button1.Enabled = false;string showText = DownloadFile(textBox1.Text, textBox2.Text);MessageBox.Show(showText);button1.Text = "下载";button1.Enabled = true;progressBar1.Value = 0;processCount = 0;}/// <summary>        /// 下载文件        /// </summary>        /// <param name="URL">下载文件地址</param>       /// <param name="Filename">下载后的存放地址</param>        public String DownloadFile(string URL, string filename){try{System.Net.HttpWebRequest myRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL);System.Net.HttpWebResponse myResponse = (System.Net.HttpWebResponse)myRequest.GetResponse();long totalBytes = myResponse.ContentLength;if (myResponse.ContentLength != 0){System.IO.Stream st = myResponse.GetResponseStream();System.IO.Stream so = new System.IO.FileStream(filename,System.IO.FileMode.Create);long totalDownloadedByte = 0;byte[] by = new byte[1024];int restSize = st.Read(by, 0, (int)by.Length);while (restSize > 0){totalDownloadedByte = restSize + totalDownloadedByte;so.Write(by, 0, restSize);restSize = st.Read(by, 0, (int)by.Length);//处理processprocessCount = (int)(100 * totalDownloadedByte / totalBytes);progressBar1.Value = processCount;}so.Close();st.Close();return "成功";}else{return "网络资源不存在";}}catch (System.Exception e){return "下载文件失败！" + e.ToString();}}private void button2_Click(object sender, EventArgs e){if (saveFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK){textBox2.Text = saveFileDialog1.FileName;}}private void Download_Load(object sender, EventArgs e){textBox2.Enabled = false;}}
}

程序界面很简洁：

项目实例已经上传，欢迎下载~