Exception codes, or detecting a "file already exists" type exception

try
{
    using (var stream = new FileStream("C:\\Test.txt", FileMode.CreateNew))
    using (var writer = new StreamWriter(stream))
    {
        //write file
    }
}
catch (IOException e)
{
    var exists = File.Exists(@"C:\Text.text"); // =)
}

Won't work for temp files etc which might have been deleted again.

Here are my exception best practices: https://coderr.io/exception-handling

You can place this condition in your catch statement for IOException: if(ex.Message.Contains("already exists")) { ... }. It is a hack, but it will work for all cases that a file exists, even temporary files and such.

Edit: there is another Hresult that is used when file already exists: 0x800700B7 (-2147024713) "Cannot create a file when that file already exists". Updated the code sample.

---

When you try to create a new file and it already exists IOException will have Hresult = 0x80070050 (-2147024816).

So you code could look like this:

try
{
    using (var stream = new FileStream("C:\\Test.txt", FileMode.CreateNew))
    using (var writer = new StreamWriter(stream))
    {
        //write file
    }
}
catch (IOException e)
{
    if (e.HResult == -2147024816 || 
        e.HResult == -2147024713)
    {
        // File already exists.
    }
}