How ASP.NET determines if a file exists on the hard drive

傻小囡

Using the built-in FileUpload control, I want to perform error handling without this file.
My code looks like this:
HttpFileCollection uploadedFiles = Request.Files;
for (int i = 0; i <uploadedFiles.Count; i ++)
{
    HttpPostedFile userPostedFile = uploadedFiles [i];
    if (File.Exists (userPostedFile.FileName))
    {
        Upload
    }
    else
    {
        Error
    }
}
The problem is that the absolute path of the file can be obtained at userPostedFile.FileName, such as: "C:\\Documents and Settings\\Admin\\Desktop\\aaa.txt", but whether the file exists or not, the result is false ..... . I don't know what's wrong with this method, or there are other better ways to determine if the file exists? Ask the master!

寒雪鸣

Show yourself the code
// Get the file name in the control
string fileName = this.txtFile.PostedFile.FileName.Substring (this.txtFile.PostedFile.FileName.LastIndexOf ("\\"));
// Set server path folder and file
string sFileName = Server.MapPath (Request.ApplicationPath) + "\\fileFavorite" + fileName;

// Get the type of file
string fileJudge = fileName.Substring (fileName.LastIndexOf (".") + 1);
if (fileJudge.Equals ("pdf") || fileJudge.Equals ("PDF") || fileJudge.Equals ("xls") || fileJudge.Equals ("XLS") ||
fileJudge.Equals ("doc") || fileJudge.Equals ("DOC") || fileJudge.Equals ("txt") || fileJudge.Equals ("TXT") ||
fileJudge.Equals ("ppt") || fileJudge.Equals ("PPT") || fileJudge.Equals ("csv") || fileJudge.Equals ("CSV"))
{
if (System.IO.File.Exists (Server.MapPath (Request.ApplicationPath) + "\\fileFavorite" + fileName) == false)
{
try
{
string newFileName = this.newFileNameUrl (); // new file name uploaded to the server
Ranch
this.txtFile.PostedFile.SaveAs (Server.MapPath (Request.ApplicationPath) + "\\fileFavorite" + "\\" + newFileName);
return true;
}
catch (Exception ex)
{
ex.GetType ();
Response.Write ("<script> onload = function () {alert ('Upload failed for network reasons!');} </ Script>");
return false;
}
}
else
{
Response.Write ("<script> onload = function () {alert ('File already exists!');} </ Script>");
return false;
}
}
else
{
Response.Write ("<script> onload = function () {alert ('The format of the file to be uploaded is incorrect!');} </ Script>");
return false;
}

zhouji700

userPostedFile.FileName is just a file name without a path

echg2002

The file name in the upload control under asp.net is a client-side file, not a server-side file. C # is running on the server side. You cannot judge whether the file exists based on this.

shenmue024

You want to determine whether the file to be saved exists, not whether the original file exists

string newPath = Server.Mappath (".. *****");

if (! File.Exists (newPath))
{
    //save.
}

zhouji700

userPostedFile.FileName is just a file name on the client, without the path
such as:
if (File.Exists ("c:\\" + userPostedFile.FileName)) // here c:\\is replaced with the directory you want to upload to
    {
        Upload
    }
    else
    {
        Error
    }

yuyi626

if (File.PostedFile.ContentLength! = 0)
{
 File.PostedFile.SaveAs ("path");
}

六零六

You cannot access the client's hard drive


Consider this security aspect.

cqgang

Judgment. ContentLength == 0
    HttpPostedFile userPostedFile = uploadedFiles [i];
    if (userPostedFile.ContentLength! = 0)
    {
        save
    }
    else
    {
        Error
    }

zhouji700

Oh, the landlord wants to determine whether the client's file exists? Then use the method upstairs
if (userPostedFile.ContentLength! = 0)