FileInfo.Exists exhibits weird behavior

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

I am seeing something I don't understand. I am creating a new file that does not exist. After instantiating StreamWriter passing the file name then FileInfo.Exists is true. Great. If I access FileInfo.Exists before the StreamWriter it is false. Great. Now if I access FileInfo.Exists before and after StreamWriter it always returns false. Why????

See comments in code

using System
using System.IO

class Bu


static void Main(

FileInfo afileinfo = new FileInfo("list.txt")
try

// if you uncomment the next lin

//bool b = afileinfo.Exists

// then Console.WriteLine prints "list.txt does NOT exist!
// even though the file exists
// Also, if you display afileinfo.Exists in the
// debug Locals window it does the same thing

StreamWriter asw = new StreamWriter("list.txt")

if ( afileinfo.Exists
Console.WriteLine("list.txt exists!")
els
Console.WriteLine("list.txt does NOT exist!")

asw.WriteLine("line")
asw.WriteLine("line")
asw.Close()
}
catch (IOException aexception)

System.Console.WriteLine(aexception.Message)
throw new NotSupportedException()

finally

afileinfo.Delete()
}

}
 
Rlzsmith said:
I am seeing something I don't understand. I am creating a new file
that does not exist. After instantiating StreamWriter passing the
file name then FileInfo.Exists is true. Great. If I access
FileInfo.Exists before the StreamWriter it is false. Great. Now if I
access FileInfo.Exists before and after StreamWriter it always
returns false. Why?????
Click to expand...

I believe it's basically caching the old value. If you create a new
FileInfo instead, it should be fine.
 
Rlzsmith said:
I am seeing something I don't understand. I am creating a new file that does not exist. After instantiating StreamWriter passing the file name then FileInfo.Exists is true. Great. If I access FileInfo.Exists before the StreamWriter it is false. Great. Now if I access FileInfo.Exists before and after StreamWriter it always returns false. Why?????

See comments in code:

using System;
using System.IO;

class Bug
{

static void Main()
{
FileInfo afileinfo = new FileInfo("list.txt");
try
{
// if you uncomment the next line

//bool b = afileinfo.Exists;

// then Console.WriteLine prints "list.txt does NOT exist!"
// even though the file exists.
// Also, if you display afileinfo.Exists in the
// debug Locals window it does the same thing.

StreamWriter asw = new StreamWriter("list.txt");

if ( afileinfo.Exists )
Console.WriteLine("list.txt exists!");
else
Console.WriteLine("list.txt does NOT exist!");

asw.WriteLine("line");
asw.WriteLine("line");
asw.Close();
}
catch (IOException aexception)
{
System.Console.WriteLine(aexception.Message);
throw new NotSupportedException();
}
finally
{
afileinfo.Delete();
}
}
}
Click to expand...

The file attribute information is cached by the FileInfo object. If the
information on the filesystem changes, you'll need to call
afileinfo.Refresh() to get updated attribute information.
 
afileinfo.Refresh()

Ahh. Ok. So why did they not program it to do a refresh on subsequent calls to Exist or other file attributes

Thanks mikeb for the explanation.
 
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