All about WP7 Isolated Storage - Read and Save Binary files

published on: 4/26/2011 | Views: N/A | Tags: IsoStore

by WindowsPhoneGeek

This is the 9th article from the "All about WP7 Isolated Storage " series of short articles focused on real practical examples with source code rather than a plain theory. I am going to talk about how to read and save Binary files into Isolated Storage.

Binary files are usually thought of as being a sequence of bytes. Generally a binary file may contain any type of data encoded in binary form. For example: .mp3 file, .jpg file, .txt file, .db, etc. can be thought as binary files.

• All about WP7 Isolated Storage - intro to Isolated Storage
• All about WP7 Isolated Storage - Creating Folders and files
• All about WP7 Isolated Storage - Store data in IsolatedStorageSettings
• All about WP7 Isolated Storage - Read and Save Text files
• All about WP7 Isolated Storage - Read and Save XML files using XmlSerializer
• All about WP7 Isolated Storage - Read and Save XML files using XmlWriter
• All about WP7 Isolated Storage - Read and Save Images
• All about WP7 Isolated Storage - Read and Save Captured Image
• All about WP7 Isolated Storage - Read and Save Binary files
• All about WP7 Isolated Storage - File manipulations
• All about WP7 Isolated Storage - Recommendations and Best Practices
• All about WP7 Isolated Storage - open source Databases and Helper libraries

To begin with lets first create a Windows Phone 7 application project and add a sample .mp3 file (in our case Battery_Low.mp3 attached at the end of this article).

After that include the following namespaces in MainPage.xaml.cs (alternatively you can use the code in another page):

using System.IO.IsolatedStorage;
using System.IO;
using System.Windows.Resources;

Save .MP3 File to Isolated Storage

In this example at first we will check if the file already exists and after that we will save the Battery_Low.mp3 file to the IsolatedStorage.

Basically at first we create a stream out of the sample .mp3 file and after that a virtual store. Next we use BinaryWriter and BinaryReader to create a new .mp3 file into Isolatedstorage(create a new file into IsolatedStorage and copy the data from Battery_Low.mp3 into the newly created one). Note that we read the file in chunks in order to reduce memory consumption and increase performance!

private const string FileName = "Battery_Low.mp3";

private void btnSave_Click(object sender, RoutedEventArgs e)
{
    StreamResourceInfo streamResourceInfo = Application.GetResourceStream(new Uri(FileName, UriKind.Relative));

    using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
    {
        if (myIsolatedStorage.FileExists(FileName))
        {
            myIsolatedStorage.DeleteFile(FileName);
        }

        using (IsolatedStorageFileStream fileStream = new IsolatedStorageFileStream(FileName, FileMode.Create, myIsolatedStorage))
        {
            using (BinaryWriter writer = new BinaryWriter(fileStream))
            {
                Stream resourceStream = streamResourceInfo.Stream;
                long length = resourceStream.Length;
                byte[] buffer = new byte[32];
                int readCount = 0;
                using (BinaryReader reader = new BinaryReader(streamResourceInfo.Stream))
                {
                    // read file in chunks in order to reduce memory consumption and increase performance
                    while (readCount < length)
                    {
                        int actual = reader.Read(buffer, 0, buffer.Length);
                        readCount += actual;
                        writer.Write(buffer, 0, actual);
                    }
                }
            }
        }
    }
}

NOTE: When working with files always use Using statement because it provides a convenient syntax that ensures the correct use of IDisposable objects.

Read .MP3 File from Isolated Storage

In this example at first open an existing Battery_Low.mp3  file from the Isolated Storage and read its content. After that the content is set as a source of  MediaElement control.

private void btnRead_Click(object sender, RoutedEventArgs e)
{
    using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
    {
        using (IsolatedStorageFileStream fileStream = myIsolatedStorage.OpenFile(FileName, FileMode.Open, FileAccess.Read))
        {
            this.mediaElement.SetSource(fileStream);
        }
    }
}

NOTE: When open an existing file from the Isolated Storage we use  FileMode.Open, when we want to read to a file we useFileAccess.Read! You can find a list of all FileAccess possibilities here.

NOTE: "mediaElement" is a MediaElement placed inside MainPage.xaml: <MediaElement x:Name="mediaElement" AutoPlay="True"/>

In this article I talked about reading and saving binary files(.mp3 file) into Isolated Storage. Here is the full source code:

Stay tuned with the rest of the posts. I hope that the article was helpful.

You can also follow us on Twitter @winphonegeek

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