Update ObjectStorage with new constructor parameter

Author: sperrat

docs/helpers/ObjectSerializer.md

@@ -0,0 +1,97 @@
+---
+title: Object Serializer
+author: simop
+description: IObjectSerializer is an interface that you can implement to provide a serializer of your choice to ObjectStorageHelper.
+keywords: windows 10, uwp, windows community toolkit, uwp community toolkit, uwp toolkit, serialization
+dev_langs:
+  - csharp
+  - vb
+---
+
+# ObjectSerializer
+
+You should implement IObjectSerializer when you need to write data using this toolkit's helpers with a custom serializer. If you don't, a default JSON serializer will be used otherwise.
+
+## Methods
+
+| Methods | Return Type | Description |
+|---------|-------------|-------------|
+| Serialize<T>(T)        | string | Serialize an object of type T into a string. |
+| Deserialize<T>(string) | T      | Deserialize a string to an object of type T. |
+
+## Examples
+
+### Json.NET
+
+```csharp
+using Microsoft.Toolkit.Uwp.Helpers;
+using Newtonsoft.Json;
+
+namespace Contoso.Helpers
+{
+    public class JsonNetObjectSerializer : IObjectSerializer
+    {
+        // Specify your serialization settings
+        private readonly JsonSerializerSettings settings = new JsonSerializerSettings();
+
+        public string Serialize<T>(T value) => JsonConvert.SerializeObject(value, typeof(T), Formatting.Indented, settings);
+
+        public T Deserialize<T>(string value) => JsonConvert.DeserializeObject<T>(value, settings);
+    }
+}
+```
+
+### DataContract
+
+```csharp
+using System.IO;
+using System.Runtime.Serialization;
+using System.Xml;
+
+namespace Contoso.Helpers
+{
+    public class DataContractObjectSerializer : IObjectSerializer
+    {
+        // Specify your serialization settings
+        private readonly DataContractSerializerSettings settings = new DataContractSerializerSettings();
+
+        public string Serialize<T>(T value)
+        {
+            var serializer = new DataContractSerializer(typeof(T), settings);
+
+            using (var stringWriter = new StringWriter())
+            using (var xmlWriter = XmlWriter.Create(stringWriter))
+            {
+                serializer.WriteObject(xmlWriter, value);
+                return stringWriter.ToString();
+            }
+        }
+
+        public T Deserialize<T>(string value)
+        {
+            var serializer = new DataContractSerializer(typeof(T), settings);
+
+            using (var stringReader = new StringReader(value))
+            using (var xmlReader = XmlReader.Create(stringReader))
+            {
+                return serializer.ReadObject(xmlReader) as T;
+            }
+        }
+    }
+}
+```
+
+## Requirements
+
+| Device family | Universal, 10.0.16299.0 or higher |
+| --- | --- |
+| Namespace | Microsoft.Toolkit.Uwp |
+| NuGet package | [Microsoft.Toolkit.Uwp](https://www.nuget.org/packages/Microsoft.Toolkit.Uwp/) |
+
+## API
+
+* [IObjectSerializer source code](https://github.com/windows-toolkit/WindowsCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp/Helpers/ObjectStorage/IObjectSerializer.cs)
+
+## Related topics
+
+* [ObjectStorage](https://docs.microsoft.com/en-us/windows/communitytoolkit/helpers/objectstorage)

docs/helpers/ObjectStorage.md

@@ -18,6 +18,14 @@ The Object Storage Helper will help you handle storage of generic objects within
 > [!div class="nextstepaction"]
 > [Try it in the sample app](uwpct://Helpers?sample=Object%20Storage)
 
+## Constructors
+
+LocalObjectStorageHelper and RoamingObjectStorageHelper have the same constructor with an optional parameter:
+
+| Constructor | Description |
+|-------------|-------------|
+| ObjectStorageHelper(IObjectSerializer = null) | Initializes a new instance of the ObjectStorageHelper class with the provided [IObjectSerializer](ObjectSerializer.md), that will be used when serializing and deserializing data in Settings or in Storage; if no serializer is provided, a default JSON serializer will be used. |
+
 ## Properties
 
 | Property | Type | Description |
@@ -219,3 +227,4 @@ Await helper.SaveFileAsync(keySimpleObject, o)
 
 * [LocalObjectStorageHelper source code](https://github.com/Microsoft/WindowsCommunityToolkit//blob/master/Microsoft.Toolkit.Uwp/Helpers/ObjectStorage/LocalObjectStorageHelper.cs)
 * [RoamingObjectStorageHelper source code](https://github.com/Microsoft/WindowsCommunityToolkit//blob/master/Microsoft.Toolkit.Uwp/Helpers/ObjectStorage/RoamingObjectStorageHelper.cs)
+* [IObjectSerializer source code](https://github.com/windows-toolkit/WindowsCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp/Helpers/ObjectStorage/IObjectSerializer.cs)

docs/toc.md

@@ -140,6 +140,7 @@
 ## [IncrementalLoadingCollection](helpers/IncrementalLoadingCollection.md)
 ## [NetworkHelper](helpers/NetworkHelper.md)
 ## [ObjectStorage](helpers/ObjectStorage.md)
+## [ObjectSerializer](helpers/ObjectSerializer.md)
 ## [PrintHelper](helpers/PrintHelper.md)
 ## [RemoteDeviceHelper](helpers/RemoteDeviceHelper.md)
 ## [StorageFileHelper](helpers/StorageFiles.md)