Use C # Builder implementation file download

Author: Xu Changyou a. Overview: This article introduces some of the basic knowledge of Internet communication programming with C # Builder through an example. We know that the .NET class contains a request / response layer, an application protocol layer, a transport layer, etc. In this program, we use the WebRequest class in the request / response layer and the WebClient class, etc. to achieve high abstract degree of Internet communication services. The function of this program is to complete the download. two. Realization Principle: The principle of program implementation is relatively simple, mainly used to use the WebClient class and the FileStream class. Where the WebClient class is in the System.Net namespace, the primary function of this class is to provide a public method for transmitting data to the URI identifier and resources from the URI identifier. We use the downfile () method to download the file to the local. The file data is then written to the local file in a data stream with an instance object of the FILESTREAM class. This completes the download of the file. three. Implementation steps: 1. First, open C # Builder, File-> New-> C # Application, Name We are set to "Download". 2. The settings for the main interface. TEXT is set to "File Download", and StartPosition is set to CENTERSCREEN, and the maximizebox is set to false. We add the following controls on the main form: two tag controls label1, label2, a text box control TextBox1, a button control Button1 and a progress bar Control Progressbar1.

Label1: Text is URL; label2: text is a download progress; TextBox1: text is set to empty; button1: text is set to download; 3. Program encoding // Process Downfile, download private void downfile () for completion files (String FileName; WebClient DownFile = new WebClient (); long fbytes; if (textBox1.Text = "!") {saveFileDialog1.ShowDialog (); FileName = saveFileDialog1.FileName; if (! FileName = "") {// get the file size WebRequest wr_request = WebRequest.Create (textBox1.Text); WebResponse wr_response = wr_request.GetResponse (); fbytes = wr_response.ContentLength; progressBar1.Maximum = (int) fbytes; progressBar1.Step = 1; wr_response.Close (); // download data starts DownFile.DownloadData (textBox1.Text); Stream strm = DownFile.OpenRead (textBox1.Text); StreamReader reader = new StreamReader (strm); byte [] mbyte = new byte [fbytes]; int allmybyte = (int) MByte.Length; Int startmbyte = 0; while (fbytes> 0) {INT m = Strm.read (mbyte, startmbyte, allmyby; if (m == 0) Break; startmbyte = m; allmybyte- = m; progressBar1.value = m;} FileStream fstrm = new FileStream (FileName, FileMode.OpenOrCreate, FileAccess.Write); fstrm.Write (mbyte, 0, startmbyte); strm.Close (); fstrm.Close ( ); Progravelbar1.value = progressbar1.maximum;}} else {messagebox.show ("No input to download)! ");}} // Double-click the" Download "button, enter the following code: Thread THREADSTART (NEWNSTART (Downfile)); th.Start (); // The complete code is as follows: use system; use system.drawing Using system.collections; using system.componentmodel; using system.windows.forms;

using System.Data; using System.Net; using System.IO; using System.Threading; namespace download {///