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asp.net中如何实现多个文件同时下载

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　　如何实现asp.net多个文件同时下载?先要读取文件夹下的文件，可能同时存在多个文件;然后选中文件，然后点击下载，同时可以选择多个文件。通过生产压缩包的形式进行下载，然后再清除压缩包，这样用户可以一次性全部下载下来。

　　一、获取目录下的所有文件，然后绑定到checkboxlist中，代码如下：

ckl_ck.Items.Clear();
DirectoryInfo TheFolder = new DirectoryInfo(Server.MapPath("Resource/Help"));
//遍历文件夹下的文件
foreach (FileInfo NextFile in TheFolder.GetFiles())

　　二、选中文件后，点击下载按钮。代码：

protected void Btn_down_Click(object sender, EventArgs e)
{
if (ckl_ck.Items.Count > 0)
{
List<string> listFJ = new List<string>();//保存附件路径
List<string> listFJName = new List<string>();//保存附件名字
for (int i = 0; i < ckl_ck.Items.Count; i++)
{
if (ckl_ck.Items[i].Selected)
{
listFJ.Add(Server.MapPath("Resource/Help/") + ckl_ck.Items[i].Text);
listFJName.Add(ckl_ck.Items[i].Text);
}

}
string time = DateTime.Now.Ticks.ToString();
ZipFileMain(listFJ.ToArray(), listFJName.ToArray(), Server.MapPath("Resource/Help/" + time + ".zip"), 9);//压缩文件
DownloadFile(Server.UrlEncode("附件.zip"), Server.MapPath("Resource/Help/" + time + ".zip"));//下载文件
}
}
private void DownloadFile(string fileName, string filePath)
{
FileInfo fileInfo = new FileInfo(filePath);
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding", "binary");
Response.ContentType = "application/octet-stream";
Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
Response.WriteFile(fileInfo.FullName);
Response.Flush();
File.Delete(filePath);//删除已下载文件
Response.End();
}

/// <summary>
/// 压缩文件
/// </summary>
/// <param name="fileName">要压缩的所有文件（完全路径)</param>
/// <param name="fileName">文件名称</param>
/// <param name="name">压缩后文件路径</param>
/// <param name="Level">压缩级别</param>
public void ZipFileMain(string[] filenames, string[] fileName, string name, int Level)
{
ZipOutputStream s = new ZipOutputStream(File.Create(name));
Crc32 crc = new Crc32();
//压缩级别
s.SetLevel(Level); // 0 - store only to 9 - means best compression
try
{
int m = 0;
foreach (string file in filenames)
{
//打开压缩文件
FileStream fs = File.OpenRead(file);//文件地址
byte[] buffer = new byte[fs.Length];
fs.Read(buffer, 0, buffer.Length);
//建立压缩实体
ZipEntry entry = new ZipEntry(fileName[m].ToString());//原文件名
//时间
entry.DateTime = DateTime.Now;
//空间大小
entry.Size = fs.Length;
fs.Close();
crc.Reset();
crc.Update(buffer);
entry.Crc = crc.Value;
s.PutNextEntry(entry);
s.Write(buffer, 0, buffer.Length);
m++;
}
}
catch
{
throw;
}
finally
{
s.Finish();
s.Close();
}
}

　　三、系统中需要引用的dll 需要下载。

　　引用文件dll：ICSharpCode.SharpZipLib.dll

　　1. 合成下载文件夹

   Protected Sub btn_down_click(ByVal sender As Object, ByVal e As EventArgs) Handles btn_Down.Click
        If txtBz.Text.Trim = "" Then
            Page.ClientScript.RegisterClientScriptBlock(Me.[GetType](), "", "alert('请填写下载备注！');", True)
            Exit Sub
        End If

        Dim i As Integer
        Dim selcount As Integer = 0
        Dim fileList As List(Of String) = New List(Of String)()
        If rptList.Items.Count > 0 Then
            For i = 0 To rptList.Items.Count - 1
                Dim chk As CheckBox = rptList.Items(i).FindControl("cbkItem")
                If chk IsNot Nothing AndAlso chk.Checked Then
                    selcount += 1
                    Dim filePath As HiddenField = rptList.Items(i).FindControl("hfUrl")
                    Dim fileName As HiddenField = rptList.Items(i).FindControl("hfFileName")

                    If filePath IsNot Nothing Then
                        Dim root As String = Request.PhysicalApplicationPath
                        Dim tmpUrl = root + filePath.Value
                        fileList.Add(tmpUrl + "|" + fileName.Value) '最后结果为：路径|名称
                    End If
                End If

            Next
        End If
        Dim time As String = DateTime.Now.Ticks.ToString()
        Dim baseFolder As String = HttpContext.Current.Request.MapPath("~/UploadFile/TempWorkFlow/")
        If Not Directory.Exists(baseFolder) Then
            Directory.CreateDirectory(baseFolder)
        End If
        If selcount = 0 Then
            Page.ClientScript.RegisterClientScriptBlock(Me.[GetType](), "", "alert('请选择要下载的文件！');", True)
            Exit Sub
        Else
            ZipFileMain(fileList.ToArray(), baseFolder & time & ".zip", 9)
            '压缩文件
            DownloadFile(Server.UrlEncode("附件.zip"), baseFolder & time & ".zip")
            'Response.Redirect("Download.aspx?FileName=" & Server.UrlEncode("附件.zip") & "&FilePath=" & baseFolder & time & ".zip")
        End If
    End Sub

　　2. 压缩下载函数

    ''' <summary>
    ''' 压缩文件
    ''' </summary>
    ''' <param name="fileName">要压缩的所有文件（完全路径)</param>
    ''' <param name="name">压缩后文件路径</param>
    ''' <param name="Level">压缩级别</param>
    Public Shared Sub ZipFileMain(filenames As String(), name As String, Level As Integer)
        Dim s As New ZipOutputStream(File.Create(name))
        Dim crc As New Crc32()
        '压缩级别
        s.SetLevel(Level)
        ' 0 - store only to 9 - means best compression
        Try
            For Each file__1 As String In filenames
                '打开压缩文件
                Dim fs As FileStream = File.OpenRead(file__1.Split("|"c)(0))
                '文件地址
                Dim buffer As Byte() = New Byte(fs.Length - 1) {}
                fs.Read(buffer, 0, buffer.Length)

                '建立压缩实体
                Dim entry As New ZipEntry(file__1.Split("|"c)(1))
                '原文件名
                '时间
                entry.DateTime = DateTime.Now
                '空间大小
                entry.Size = fs.Length
                fs.Close()
                crc.Reset()
                crc.Update(buffer)
                entry.Crc = crc.Value
                s.PutNextEntry(entry)
                s.Write(buffer, 0, buffer.Length)
            Next
        Catch
            'Throw
        Finally
            s.Finish()
            s.Close()
        End Try
    End Sub

　　3. 压缩下载函数