From the code snippet above what I understand you are passing invalid filename and arguments to the myProcess.
It should be like
myProcess.StartInfo.FileName = "C:\\Program Files\\Symantec\\Symantec Endpoint Protection\\DoScan.exe";
string myprocarg = " /cmdlinescan " + strFile + "/LOGFILE=\\" + strFilePath + "\\Logs\\" + Path.GetFileName(strFile) + ".log\"";
myProcess.StartInfo.Arguments = myprocarg;
myProcess.Start();
Please try and like the answer if it works.
All the Best.
Kiran