Saving files on Raspberry PI with Windows IoT

问题

I have a question about saving files on Raspberry PI with Windows IoT.

What I want to do: I have various values (temperature) which I want to log. The easiest way for me would be, to write a simple txt-file with all the values.

First of all: Is it even possible to create a file locally on the SD card? Because the code samples I found only work on a "normal" Windows system:

        if (!File.Exists(path))
    {
        // Create a file to write to.
        string createText = "Hello and Welcome" + Environment.NewLine;
        File.WriteAllText(path, createText);
    }

or on Windows Phone:

      public void createdirectory()
    {
        IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication();
        myIsolatedStorage.CreateDirectory("TextFilesFolder");
        filename = "TextFilesFolder\\Samplefile.txt";
        Create_new_file();
    }

    public void Create_new_file()
    {
        IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication();

        if (!myIsolatedStorage.FileExists(filename))
        {
            using (StreamWriter writeFile = new StreamWriter(new IsolatedStorageFileStream(filename, FileMode.Create, FileAccess.Write, myIsolatedStorage)))
            {
                string someTextData = "This is a test!";
                writeFile.WriteLine(someTextData);
               // writeFile.Close();
            }
        }

The code for Windows Phone makes more sense to me. (The other doesn't work at all anyway). But even the phone code is the correct one, I have no idea how to get an access to the internal storage. I've tried the IsolatedStorageExplorerTool, but it doesn't recognize my device. Probably because my device is not connected with USB... and it's not a phone. When I use SSH I also can't find the directory.

Maybe someone has an idea. In advance thanks for your help!

回答1:

Nevermind, I found the solution. 1. It's the code for Windows phone. 2. You have to use the Windows IoT Core Watcher. Right click on your device and open the network share. Afterwards I found the text file at: \\c$\Users\DefaultAccount\AppData\Local\Packages\\LocalState\TextFilesFolder

回答2:

You can use serialization for organized storage than textual storage.

I'm attaching static class file that contains method to serialize and de-serialize back to the original object.

Download Source Code

Let's take a generalize example. Assume, you have Student and Mark class as below:

/// <summary>
/// Provides structure for 'Student' entity
/// </summary>
/// 'DataContract' attribute is necessary to serialize object of following class. By removing 'DataContract' attribute, the following class 'Student' will no longer be serialized
[DataContract]
public class Student
{
    [DataMember]
    public ushort Id { get; set; }

    [DataMember]
    public string UserName { get; set; }

    /// <summary>
    /// Password has been marked as non-serializable by removing 'DataContract'
    /// </summary>
    // [DataMember] // Password will not be serialized. Uncomment this line to serialize password
    public string Password { get; set; }

    [DataMember]
    public string FirstName { get; set; }

    [DataMember]
    public string LastName { get; set; }

    [DataMember]
    public List<Mark> Marks { get; set; }
}

[DataContract]
public class Mark
{
    [DataMember]
    public string Subject { get; set; }

    [DataMember]
    public short Percentage { get; set; }
}

Make sure to attribute '[DataContract]' on calss and '[DataMember]' on data member to serialize them else they will be ignore while serializing object

Now, to serialize and deserialize, you will have following static class with Save and Load function:

/// <summary>
/// Provides functions to save and load single object as well as List of 'T' using serialization
/// </summary>
/// <typeparam name="T">Type parameter to be serialize</typeparam>
public static class SerializableStorage<T> where T : new()
{
    public static async void Save(string FileName, T _Data)
    {
        MemoryStream _MemoryStream = new MemoryStream();
        DataContractSerializer Serializer = new DataContractSerializer(typeof(T));
        Serializer.WriteObject(_MemoryStream, _Data);

        Task.WaitAll();

        StorageFile _File = await ApplicationData.Current.LocalFolder.CreateFileAsync(FileName, CreationCollisionOption.ReplaceExisting);

        using (Stream fileStream = await _File.OpenStreamForWriteAsync())
        {
            _MemoryStream.Seek(0, SeekOrigin.Begin);
            await _MemoryStream.CopyToAsync(fileStream);
            await fileStream.FlushAsync();
            fileStream.Dispose();
        }
    }

    public static async Task<T> Load(string FileName)
    {
        StorageFolder _Folder = ApplicationData.Current.LocalFolder;
        StorageFile _File;
        T Result;

        try
        {
            Task.WaitAll();
            _File = await _Folder.GetFileAsync(FileName);

            using (Stream stream = await _File.OpenStreamForReadAsync())
            {
                DataContractSerializer Serializer = new DataContractSerializer(typeof(T));

                Result = (T)Serializer.ReadObject(stream);

            }
            return Result;
        }
        catch (Exception ex)
        {
            return new T();
        }
    }
}

Now, let's see how to store object of a Student and retrieve it back from file:

/* Create an object of Student class to store */
Student s1 = new Student();
s1.Id = 1;
s1.UserName = "Student1";
s1.Password = "Student123";
s1.FirstName = "Abc";
s1.LastName = "Xyz";
s1.Marks = new List<Mark>();

/* Create list of Marks */
Mark m1 = new Mark();
m1.Subject = "Computer";
m1.Percentage = 89;

Mark m2 = new Mark();
m2.Subject = "Physics";
m2.Percentage = 92;

/* Add marks into Student object */
s1.Marks.Add(m1);
s1.Marks.Add(m2);

/* Store Student object 's1' into file 'MyFile1.dat' */
SerializableStorage<Student>.Save("MyFile1.dat", s1);

/* Load stored student object from 'MyFile1.dat' */
Student s2 = await SerializableStorage<Student>.Load("MyFile1.dat");

You can serialize and de-serialize any class. To store object of a class other than 'Student', suppose 'MyClass', just replace Student type from 'T' parameter of the function as below:

/* Store MyClass object 's1' into file 'MyFile1.dat' */
SerializableStorage<MyClass>.Save("MyFile1.dat", s1);

/* Load stored MyClass object from 'MyFile1.dat' */
MyClass s2 = await SerializableStorage<MyClass>.Load("MyFile1.dat");

NOTE: 'MyFile1.dat' will be stored in 'ApplicationData.Current.LocalFolder'. This code is tested on Windows 10 IoT Core (10.0.10586.0) and can work on any UWP app.

Download Source Code

来源：https://stackoverflow.com/questions/34385625/saving-files-on-raspberry-pi-with-windows-iot

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