Question

In windows phone 7, what is the protocol for updated an isolated storage text file? Say I have 10 words in a text file arranged at 1 per line. Now suppose, the user uses the application and a new word needs to be stored on the fifth line. How do I write to the file, which already contains 10 words with 1 word per line?

Thanks in advance you guys are awesome.

Answer 1

The way I have been doing it is:

1. Read in a file from IsolatedStorage to menmory
2. Update the String
3. Write the file back to storage

Read in File

public static string ReadFromStorage(string filename)
{
    string fileText = "";
    try
    {
        using (IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            using (StreamReader sr = new StreamReader(new IsolatedStorageFileStream(filename, FileMode.Open, storage)))
            {
                fileText = sr.ReadToEnd();
            }
        }
    }

    catch
    {
    }

    return fileText;
}

Write to File

public static void WriteToStorage(string filename, string text)
{
    try
    {
        using (IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            string directory = Path.GetDirectoryName(filename);
            if (!storage.DirectoryExists(directory))
                storage.CreateDirectory(directory);

            if (storage.FileExists(filename))
            {
                MessageBoxResult result = MessageBox.Show(filename + " Exists\nOverwrite Existing File?", "Question", MessageBoxButton.OKCancel);

                if (result == MessageBoxResult.Cancel)
                    return;
            }

            using (StreamWriter sw = new StreamWriter(storage.CreateFile(filename)))
            {
                sw.Write(text);
            }
        }
    }

    catch
    {
    }
}

So I would do:

string fileName = "Test.txt";
string testFile = IsolatedStorage_Utility.ReadFromStorage(fileName);
testFile = testFile.Replace("a", "b");
IsolatedStorage_Utility.WriteToStorage(fileName, testFile);