基于 Web 的 FTP 客户端

• 下载源代码 - 31.3 KB

引言

Microsoft .NET 框架提供了一个强大的库来访问 FTP 站点及其内容。 在本文中，我们将讨论如何从 Web 应用程序中访问它们，并从 FTP 流式传输文件并将其转储到您想要的位置。

使用代码

代码分为两部分

• FTP 助手 - 包含 FTP 方法文件的项目。
• FTP Web - 用于 FTP 的 Web 应用程序。

由于我在 ViewState 中使用它，因此必须序列化 FTPConnection 类。

[Serializable]
public class FTPConnection

以下是用于连接到 FTP 站点的方法

public FtpWebRequest ConnectToFtp(string Method)
{
    FtpWebRequest ftpRequest = (FtpWebRequest)FtpWebRequest.Create(new Uri(_url));
    ftpRequest.UseBinary = true;
    ftpRequest.Credentials = new NetworkCredential(_username, _password);
    ftpRequest.Method = Method;
    ftpRequest.Proxy = null;
    ftpRequest.KeepAlive = false;
    ftpRequest.UsePassive = false;
    return ftpRequest;
}

现在我们可以获取文件列表，包括名称和完全限定路径，来自特定 URL

/// <summary>
/// Get all files in ftp folder
/// </summary>
/// <param name="FolderUrl"></param>
/// <returns></returns>
public Dictionary<string, string> GetFileList(string FolderUrl)
{
    StringBuilder filesstring = new StringBuilder();
    WebResponse webResponse = null;
    StreamReader sreader = null;
     /// I use string type Dictionary to get both filename and filename with path
    Dictionary<string, string> Files = new Dictionary<string, string>();
    try
    {
        //you can change url to connect to ftp according to your need
        FtpWebRequest ftpRequest = ConnectToFtp(FolderUrl, 
                       WebRequestMethods.Ftp.ListDirectory);

        webResponse = ftpRequest.GetResponse();
        sreader = new StreamReader(webResponse.GetResponseStream());
        string strline = sreader.ReadLine();
        while (strline != null)
        {
            //Add filename and filename with path to dictionary
            Files.Add(strline, FolderUrl +"/"+ strline);                
        }         
       
        return Files;
    }
    catch (Exception ex)
    {
        //do any thing with exception
        return null;
    }
    finally
    {
        if (sreader != null)
        {
            sreader.Close();
        }
        if (webResponse != null)
        {
            webResponse.Close();
        }
    }
}

以下是如何获取可下载文件的字节

public byte[] DownloadFileFromFtp(string fileUrl)
{
    StringBuilder filesstring = new StringBuilder();
    WebResponse webResponse = null;
    try
    {
        FtpWebRequest ftpRequest = ConnectToFtp(fileUrl, 
                                     WebRequestMethods.Ftp.DownloadFile);
        ftpRequest.UseBinary = true;
        webResponse = ftpRequest.GetResponse();

        FtpWebResponse response = (FtpWebResponse)webResponse;
        
        Stream dfileResponseStream = response.GetResponseStream();
        
        
        int Length = 1024;
        
        Byte[] buffer = new Byte[Length];
        // collect all bytes of file
        List<byte> filebytes = new List<byte>();
        int bytesRead = dfileResponseStream.Read(buffer, 0, Length);
        while (bytesRead > 0)
        {
            for(int i= 0;i<bytesRead;i++)
            // read file byte in buffer and add it to list
                filebytes.Add(buffer[i]);
            
            bytesRead = dfileResponseStream.Read(buffer, 0, Length);
        }
        response.Close();
        return filebytes.ToArray(); // return complete byte array
    }
    catch (Exception ex)
    {
        //do any thing with exception
        return null;
    }
    finally
    {
        if (webResponse != null)
        {
            webResponse.Close();
        }
    }
}

我们完成了基本的 FTP 方法。 现在我们将查看 Web 应用程序部分。

我将 FTPHelper.FTPConnection 对象存储在 ViewState 中，因为我想在页面上多次使用相同的实例。

public FTPHelper.FTPConnection FTP
{
    set
    {
        ViewState["FTP"] = value;
    }
    get
    {
        return ViewState["FTP"] == null ? null : 
          (FTPHelper.FTPConnection)ViewState["FTP"];
    }
}

使用下面的界面设置 FTP 站点的 FTP URL、用户名和密码

现在连接到 FTP 站点并检索根目录和文件

public void ConnectToFtp()
{
    try
    {
       FTP = new FTPHelper.FTPConnection(txtFTPUrl.Text.ToLower().Replace(
                  "ftp://",""), txtUser.Text, txtPassword.Text);
        Dictionary<string, string> Files = FTP.GetFileList(FTP._url);
       
        lblWelcome.Text = "<strong> Welcome </strong> " + txtUser.Text;
        tbLogin.Visible = false;
        foreach (string ky in Files.Keys)
        {
            TreeNode trParent = new TreeNode();
            trParent.Text = (string)ky; // file name
            trParent.Value = Files[ky]; // fully qualified name

            trVFiles.Nodes.Add(trParent);
        }
    }
    catch(Exception ex)
    {
        tbLogin.Visible = false;
        lblWelcome.Text = ex.Message;
        lblWelcome.ForeColor = System.Drawing.Color.Red;
    }
}

捕获 TreeView 控件的 SelectedNodeChanged 事件，以获取所选目录节点中的目录和文件

protected void trVFiles_SelectedNodeChanged(object sender, EventArgs e)
{
     Dictionary<string,string> _filesInFolder = FTP.GetFileList(trVFiles.SelectedValue);
     Dictionary<string, string> _onlyfiles = new Dictionary<string, string>();

     foreach (string key in _filesInFolder.Keys)
     {
         // checking if file is directory 
         if (key.IndexOf('.') == -1)
         {
             TreeNode trParent = new TreeNode();
             trParent.Text = (string)key;
             trParent.Value = _filesInFolder[key];

           // appending directory to selected parent directory
             trVFiles.SelectedNode.ChildNodes.Add(trParent); 
         }
         else
         {
             _onlyfiles.Add(key, _filesInFolder[key]); // seperate the files 
         }
     }
     trVFiles.SelectedNode.Expand(); //expand the selected node
     BindGrid(_onlyfiles); // bind the grid with files separated
}

最后，获取 RowCommand 事件以下载所需的文件

protected void grdDetailView_RowCommand(object sender, GridViewCommandEventArgs e)
{
    //CommandArgument contain the fully qualified name of the file
    byte[] _downFile = FTP.DownloadFileFromFtp(e.CommandArgument.ToString());
    string _fname =e.CommandArgument.ToString();
    Response.ContentType = "application/"+_fname.Split('.')[1];
    Response.AddHeader("Content-disposition", 
                       "attachment; filename=" + _fname);
    // stream the file byte on ftp
    Response.OutputStream.Write(_downFile, 0, _downFile.Length);
    Response.End();
}

就是这样。