c#之"The process can not access the file ' ... ' because it is being used by another process"重新创建临时文件以使用 FtpWebRequest 上传

我正在通过 FTP 上传文件。起初它工作正常，但是当我第二次点击上传按钮时它会抛出错误

The process can not access the file '...' because it is being used by another process

代码如下

using (StreamWriter sw = new StreamWriter(filename, false)) //THIS LINE THROWS ERROR 
{ 
    if (dt.Rows.Count > 0) 
    { 
        sw.Write("Column1,Column2"); 
        sw.Write(sw.NewLine); 
 
        foreach (DataRow dr in dt.Rows) 
        { 
            sw.Write(dr["Column1"].ToString()); 
            sw.Write(","); 
            sw.Write(dr["Column2"].ToString()); 
            sw.Write(","); 
        } 
        sw.Close(); 
        sw.Dispose(); 
    } 
    else 
    { 
        sw.Close(); 
        sw.Dispose(); 
    } 
} 

我正在将文件保存在 csv 中，谁能帮帮我!!为什么我第二次收到此错误？

以下是上传到FTP的代码

public void UploadToFTP() 
{ 
     string fileName = "ReportName"; 
     string propfilename = Server.MapPath("~") + fileName + ".csv"; 
 
     string FtpUserid = null; 
     string FtpPwd = null; 
     string sourcePath = string.Empty; 
     string destPath = string.Empty; 
     string fName = string.Empty; 
     FtpUserid = "abc"; 
     FtpPwd = "abc"; 
 
     fName = fileName + ".csv"; 
 
     destPath = ConfigurationManager.AppSettings["destipath"].ToString(); 
     destPath = destPath.Insert(destPath.LastIndexOf("/") + 1, fName); 
 
     FtpWebRequest requestFileExists = (FtpWebRequest)WebRequest.Create(destPath); 
 
     //GET DATA IN CSV 
     UploadFTPCode(FtpUserid, FtpPwd, sourcePath, destPath, false); 
 } 
 
private void UploadFTPCode(string FtpUserid, string FtpPwd, string sourcePath, string destPath) 
{ 
     FtpWebRequest request = (FtpWebRequest)WebRequest.Create(destPath); 
     request.Method = WebRequestMethods.Ftp.UploadFile; 
     request.Credentials = new NetworkCredential(FtpUserid, FtpPwd); 
     request.Proxy = null; 
     request.UseBinary = false; 
     request.UsePassive = true; 
     request.KeepAlive = false; 
     request.Timeout = 500000; 
 
     // Copy the contents of the file to the request stream. 
     StreamReader sourceStream = new StreamReader(sourcePath); 
     byte[] fileContents = Encoding.UTF8.GetBytes(sourceStream.ReadToEnd()); 
     sourceStream.Dispose(); 
     sourceStream.Close(); 
     request.ContentLength = fileContents.Length; 
 
     Stream requestStream = request.GetRequestStream(); 
     requestStream.Write(fileContents, 0, fileContents.Length); 
     requestStream.Flush(); 
     requestStream.Close(); 
     requestStream.Dispose(); 
     sourceStream.Close(); 
 } 

请您参考如下方法:

像这样处理文件后尝试调用垃圾回收:

GC.Collect();