C# - APP: Exception: The operation was canceled.

[strakamichal]

Hi all,
i need help with one exception. I know only .Message of this exception and i know which part of code throws it.


Message:
.Message: "The operation was canceled."




Code:

try
                        {
                            FileIOPermission perm = new FileIOPermission(FileIOPermissionAccess.Write, file_name);
                            perm.Assert();
                            if (!additive && File.Exists(file_name)) File.Delete(file_name);
                            using(FileStream fs = new FileStream(file_name, FileMode.OpenOrCreate, FileAccess.ReadWrite))
                            {
                                using(StreamWriter writer = new StreamWriter(fs))
                                {
                                    writer.BaseStream.Seek(0, SeekOrigin.End);
                                    writer.Write(content);
                                    writer.Flush();
                                    writer.Close();
       
                                    result = true;
                                }
                                fs.Close();
                            }
                            CodeAccessPermission.RevertAssert();
                        }
                        catch (System.Exception err)
                        {
                            System.Diagnostics.Debug.WriteLine(err.Message);
                            throw(err);
                        }

FYI: This Windows application runs for many years, but once this error was occured and stored in log. Can somebody help me? Is anythere List of exception messages, where I can find what does the exception mean?