Why does file creation fail in Application_Start? - asp.net

Question

I have some code which attempts to create and write to a log file in a subdirectory of my website (shown below). If I put the first call to this code in the Page_Load() event of Default.aspx, it works fine every time. If, however, I make the first call to this code inside the Global.asax Application_Start() event, I get an access denied exception from .NET IO library, even though the path displayed in the exception message is correct.
Has anyone encountered anything like this? It is as if the code running from Application_Start() has a more limited set of permissions than code running later.
Kind wishes ~ Patrick
using( StreamWriter writer = new StreamWriter( FullPathAndNameData, true ) )
{
string logEntry = DateTime.Now.ToString() + ": " + formattedMessage;
writer.WriteLine( logEntry );
writer.Flush();
}

Answer 1

As far as I know, Application_Start doesn't have special permission.
Only thing I can think of is if you move the code inside Application_Start, the file path is moved outside of Web Application and it needs permission.
You can try using HttpRuntime.AppDomainAppPath.
public class Global : HttpApplication
{
private void Application_Start(object sender, EventArgs e)
{
var fullPathAndNameData = string.Format("{0}App_Data\\Log.txt",
HttpRuntime.AppDomainAppPath);
using (var writer = new StreamWriter(fullPathAndNameData, true))
{
string logEntry = DateTime.Now + ": " + "Inside Application_Start";
writer.WriteLine(logEntry);
writer.Flush();
}
}
}