Storing values in local database

Question

How can we store values i.e., username and password in local database in xamarin.forms.

I am using Write device platform specific code in Xamarin.Forms

Answer 1

I have done this before using dependency injection.

First create an interface that you will implement in your android and iOS projects

public interface UserInterface
{
    void saveUserName(string userName);
    string loadUserName();
}

Then implement that interface in both android and iOS projects

Android:

[assembly: Xamarin.Forms.Dependency (typeof (ChessUser_Android))]
public class ChessUser_Android : Java.Lang.Object, UserInterface {

    public void saveUserName(string userName){
        var prefs = Application.Context.GetSharedPreferences("MyApp", FileCreationMode.Private);
        var prefEditor = prefs.Edit();
        //save user's properties for a specific key
        prefEditor.PutString("user_name",userName);
        prefEditor.Commit();
    }

    public string loadUserName(){
        var prefs = Application.Context.GetSharedPreferences("MyApp",     FileCreationMode.Private); 
        return prefs.GetString("user_name",null);
    }

}

iOS

[assembly: Xamarin.Forms.Dependency (typeof (ChessUser_iOS))]
public class ChessUser_iOS : UserInterface {

    public void saveUserName(string userName){
       var prefs = NSUserDefaults.StandardUserDefaults;
       //save user's properties for a specific keys
       prefs.SetValueForKey (new NSString (userName), new NSString ("user_name"));
    }

    public string loadUserName(){
         var prefs = NSUserDefaults.StandardUserDefaults;
         return prefs.StringForKey ("username");
    }
}

when I want to save or load data i.e., username and password

DependencyService.Get<UserInterface>().loadUserName();
DependencyService.Get<UserInterface>().saveUserName("name");

Answer 2

While full SQLite support shown in the other answers are all great, here's an alternative if you just need simple key value storage (ex: username and passwords). It abstracts NSUserDefaults (iOS) and SharedPreferences (Android).

Shared Project

public interface ISimpleStorage
    {
        void Set(string key, string value);
        string Get(string key);
        void Delete(string key);
    }

iOS Project

[assembly: Dependency(typeof(SimpleStorage))]
namespace MyApp.iOS
{
    public class SimpleStorage : ISimpleStorage
    {
        public void Set (string key, string value)
        {
            NSString newKey = new NSString (key);
            NSString newValue = new NSString (value);

            NSUserDefaults.StandardUserDefaults.SetValueForKey (newValue, newKey);
        }

        public string Get (string key)
        {
            NSString newKey = new NSString (key);
            NSString value = (NSString)NSUserDefaults.StandardUserDefaults.ValueForKey (newKey);

            return value != null ? value.ToString () : null;
        }

        public void Delete (string key)
        {
            NSString newKey = new NSString (key);
            NSUserDefaults.StandardUserDefaults.RemoveObject (newKey);
        }
    }
}

Android

[assembly: Dependency(typeof(SimpleStorage))]
namespace MyApp.Android
{
    public class SimpleStorage : ISimpleStorage
    {
        public void Set (string key, string value)
        {
            var prefs = Forms.Context.GetSharedPreferences("MyApp", FileCreationMode.Private);
            var prefEditor = prefs.Edit();

            prefEditor.PutString (key, value);
            prefEditor.Commit();
        }

        public string Get (string key)
        {
            var prefs = Forms.Context.GetSharedPreferences("MyApp", FileCreationMode.Private);              

            return prefs.GetString(key, null);
        }

        public void Delete (string key)
        {
            var prefs = Forms.Context.GetSharedPreferences("MyApp", FileCreationMode.Private);              
            var prefEditor = prefs.Edit ();

            prefEditor.Remove (key);
            prefEditor.Commit();
        }
    }
}

I then have a helper class in my Shared project that looks like this:

public static class Device
    {
        public static ISimpleStorage Storage { get { return DependencyService.Get<ISimpleStorage> ();}}
    }

I then can use this throughout my shared code as follows:

var username = Device.Storage.Get ("username");
Device.Storage.Set ("username", textEntry.Text);
Device.Storage.Delete ("username");

Answer 3

Xamarin has a guide for using SQLite with Xamarin Forms