HTTPRequest.Files.Count Never Equals Zero

Question

I have a form on an HTML page that a user needs to use to upload a file which posts to an ASPX page. In the code behind, I want to test if a file has actually been loaded.

if (Request.Files.Count > 0)
{
    DoStuff(Request.Files[0]);
}
else
{
    throw new Exception("A CSV file must be selected for upload.");
}

I am never getting to the else. Is this just how ASP.NET operates? If I have a input element of type file, is it always going to upload a "file" even if one is not selected?

What's the proper way to do this? Maybe this?

if (Request.Files.Count > 0 && Request.Files[0].ContentLength > 0)
{
    DoStuff(Request.Files[0]);
}
else
{
    throw new Exception("A CSV file must be selected for upload.");
}

Answer 1

Maybe just this will do:

if (Request.Files.Count > 0 && Request.Files[0].ContentLength > 0)
{
    DoStuff(Request.Files[0]);
}
else
{
    throw new Exception("A CSV file must be selected for upload.");
}

Answer 2

Request.Files.Count always contains the no. of <input type="file"> elements in your form, wrapped in a Key:Value store.

Hence, if your posted form does not contain any <input type="file"> tags, then Request.Files.Count will return 0.

Each Key is the name of the <input type="file" name="OneOfTheKeys"> and the value is of type HttpPostedFileWrapper.

See here to learn about HttpPostedFileWrapper.

Answer 3

You should use the FileUpload control and check .HasFiles to see if anything was uploaded.

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.fileupload.aspx

Answer 4

I would also make sure that the data being return by the .count method is not a string. A string value of '0' is always greater than a int value of 0; which would always return true in that condition.

I would try typecasting the .count return as an int to make sure that proper types are being compared. Even a string '-1' has a higher bit value than int zero.

just a thought, though I could be wrong....