save file to network path + file encoding

Dear all,
need to correct this code  , to save file to network path :

				var permissionSet = new PermissionSet(PermissionState.None);
				var writePermission = new FileIOPermission(FileIOPermissionAccess.Write , string.Format("{0}/{1}", sPath, FileName));
				permissionSet.AddPermission(writePermission);

				if (permissionSet.IsSubsetOf(AppDomain.CurrentDomain.PermissionSet))
				{
					using (FileStream fstream = new FileStream(String.Format("{0}/{1}", sPath, FileName) ,   FileMode.Create  ))
					using (StreamWriter writer = new StreamWriter(fstream   ))
					{
						// try catch block for write permissions 					    
							
							writer.WriteLine(contents);
						

					}
				}
				else
				{
					//perform some recovery action here
				 }

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when I run this code I got error :
Access to the path '\\xxxx\xxxxx\yyyyy\text.txt' is denied. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost) at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy) at System.IO.FileStream..ctor(String path, FileMode mode) in :line 319


Also how to set file encoding.
Thanks