c# - Will using System.IO.StreamWriter & WriteLineAsync wait for a file that is being accessed by another thread -

i have following code inside asp.net mvc-5 web application :-

system.io.streamwriter file = new system.io.streamwriter(server.mappath("~/logs/logs.txt"), true); await file.writelineasync("execution started @ " + system.datetime.now.tostring()); file.close(); 

now question happen if 2 methods execute above code @ same time? 1 of them fail ? since trying write txt file being accessed thread ?

you can leverage tpl dataflow nicely such queue , mechanism writes file never occur in parallel (by using maxdegreeofparallelism)

public class logger {     private actionblock<string> block;     public logger(string filepath)     {         block = new actionblock<string>(async message => {             using(var f = file.open(filepath, filemode.openorcreate, fileaccess.write))             {                 f.position = f.length;                 using(var sw = new streamwriter(f))                 {                     await sw.writelineasync(message);                 }             }         }, new executiondataflowblockoptions{maxdegreeofparallelism = 1});     }     public void log(string message)     {         block.post(message);     } }