Read a file within a specified time

[Markus Freitag]

Hello,
I send a request via file.
After a specified time, I must read the answer and delete this file.
I make it this way.
I'm not sure that await, async is right.
The user input must be operable, but I can only continue the process after an answer.
Please look here // ####A
Because of the await is waited, thus a behavior like synchronously, the user interface remains however operable. Do I see that correctly?
Can you check it out, possibly improve it? Thanks in advance.

Thanks for tips.
Greetings Markus

//Event from a Button.
private async void FileReadOrTimeout(object sender, RoutedEventArgs e)
{
try
{
// ####A
var ret = await ReadDataAsync(@"C:\Users\Freitag\Documents\TEST_M_3.xml", 6000);

string converted = Encoding.UTF8.GetString(ret, 0, ret.Length);
converted = RemoveBom(converted);

MessageBox.Show(converted + "\n \nEnd");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}

private async Task<byte[]> ReadDataAsync(string pDatei, int pTimeOutMs)
{
int n = 0;
int m = (int)Math.Ceiling(pTimeOutMs / 100.0);

while (!File.Exists(pDatei))
{
await Task.Delay(100);
n++;
if (n == m)
throw new FileNotFoundException();

}

FileInfo fi = new FileInfo(pDatei);
Stream streamXML;

byte[] data = new byte[fi.Length];
using (var fs = fi.OpenRead())
{
int read = await fs.ReadAsync(data, 0, data.Length);

read = data?.Length ?? throw new ArgumentNullException(); // ## Needed?

streamXML = new MemoryStream(data);

var gpx = Deserialize<Msg>(streamXML);

return data;
}
}
//######################################################

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