File Read-Write Error in iOS

I have used following code for file reading and writing.

private void StorePuzzleData ()
	{
		FileInfo fileInfo = new FileInfo (Application.persistentDataPath + "\\" + difficultyLevel + puzzleId + ".txt");

		if (fileInfo.Exists)
			fileInfo.Delete ();

		string fileData = string.Empty;

		foreach (CellInformation cellInfo in cellInfoList)
			fileData += cellInfo.RowIndex + "#" + cellInfo.ColIndex + "#" + cellInfo.number + "#" + cellInfo.CellColor + "#" + cellInfo.CellDisplayColor + "#" + (cellInfo.IsGroupComplete ? 1 : 0) + ",";

		StreamWriter streamWriter = fileInfo.CreateText ();
		streamWriter.WriteLine (fileData);
		streamWriter.Close ();

		DataStorage.StorePuzzleTimePassed (difficultyLevel, puzzleId, GameController.gamePlayTime);

	}

	private void ReadPuzzleData ()
	{
		// format:  rownumber, colnumber, number, cellcolor, celldisplaycolor, isgroupcomplete

		StreamReader streamReader = File.OpenText (Application.persistentDataPath + "\\" + difficultyLevel + puzzleId + ".txt");
		string fileData = streamReader.ReadLine ();
	}

But I am getting following error in actual iOS device running. This code working correct in iMac as well in android device.

Please give me some suggestion what changes I need to do to make this correct.

Thanks to Maximilian Gerhardt for giving me this answer.

File Read-Write Error in iOS

The correct way to always generate the correct path is to use the Path.Combine(string, string) function. This will combine two paths using the correct directory path seperator, which can also be seperatly accessed through Path.DirectorySeparatorChar.

using System.IO; /* must be imported */

 private void StorePuzzleData ()
 {
     FileInfo fileInfo = new FileInfo (Path.Combine(Application.persistentDataPath, difficultyLevel + puzzleId + ".txt"));

     if (fileInfo.Exists)
         fileInfo.Delete ();

     string fileData = string.Empty;

     foreach (CellInformation cellInfo in cellInfoList)
         fileData += cellInfo.RowIndex + "#" + cellInfo.ColIndex + "#" + cellInfo.number + "#" + cellInfo.CellColor + "#" + cellInfo.CellDisplayColor + "#" + (cellInfo.IsGroupComplete ? 1 : 0) + ",";

     StreamWriter streamWriter = fileInfo.CreateText ();
     streamWriter.WriteLine (fileData);
     streamWriter.Close ();

     DataStorage.StorePuzzleTimePassed (difficultyLevel, puzzleId, GameController.gamePlayTime);

 }

 private void ReadPuzzleData ()
 {
     // format:  rownumber, colnumber, number, cellcolor, celldisplaycolor, isgroupcomplete

     StreamReader streamReader = File.OpenText (Path.Combine(Application.persistentDataPath, difficultyLevel + puzzleId + ".txt"));
     string fileData = streamReader.ReadLine ();
 }