数据序列化程序已针对Windows Metro更新（译文）

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04月16日, 2012 - 3 分钟阅读 - 1074 个词 阅读量 0

数据序列化程序已针对Windows Metro更新（译文）

原文地址：https://www.codeproject.com/Articles/367042/Data-Serializer-updated-for-Windows-Metro

原文作者：Joel Ivory Johnson

译文由本站翻译

前言

Windows Metro的数据序列化程序更新.

大约一年前,我共享了一个简单的实用程序类,用于在Windows Phone 7上保存可序列化的数据.我刚刚更新了Windows 8 Metro的组件.通过使用条件编译器指令,它仍然保留与Windows Phone 7的兼容性.在Windows Phone 7上,我更改了类,使其为静态(因此无需实例化). 对于Metro,方法是异步的.为了保存,可以传递一个动作,一旦保存操作完成,该动作将被调用.加载数据时,您将要传递一个操作,该操作将接收已加载的数据,以及一个异常参数,如果无法加载数据,则将填充该参数. 作为代码工作方式的一个示例(及其用法所依赖的平台差异),这里是我使用该程序的程序中的一种方法.该程序可在Windows Phone 7和Windows Metro上编译.

public void LoadAccess()
{
#if SILVERLIGHT
    AccessInfo = DataSaver<AccessInfo>.LoadMyData("_accessToken.xml");
#endif

#if NETFX_CORE
    DataSaver<AccessInfo>.LoadDataAsync("_accessToken.xml", (info, exc)=>
    {
        if (info != null)
        {
            this.AccessInfo = info;
        }
    });
#endif
}

public void SaveAccessToken()
{
    if (this.AccessInfo != null)
    {
#if NETFX_CORE
        DataSaver<AccessInfo>.SaveMyDataAsync(this.AccessInfo, "_accessToken.xml");
#endif
#if SILVERLIGHT
       DataSaver<AccessInfo>.SaveMyData(AccessInfo, "_accessToken.xml");
#endif
    }
}

如果您从未见过#if/#endif指令,则该指令实际上是根据某种条件有条件地注释掉代码段的.在这种情况下,条件是要定义某些编译器常量.将为各种项目类型自动创建一些常量.如果创建Windows Phone项目,则将定义" WINDOWS_PHONE"和" SILVERLIGHT"常量.对于Windows 8 Metro项目,定义了NETFX_CORE常量.当您在Visual Studio IDE中查看代码时,由于有条件的编译语句,它将使所有将被忽略的代码均灰显. 以下是序列化器的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.Text;

using System.IO;
#if SILVERLIGHT
using System.IO.IsolatedStorage;
#endif

#if NETFX_CORE
using System.Threading.Tasks;
using Windows.Storage;
using Windows.Storage.Streams;
#endif

namespace J2i.Net.Utility
{


    public class DataSaver<MyDataType>
    {

        static List<Type> _knownTypeList = new List<Type>();
        public static List KnownTypeList
        {
            get
            {
                return _knownTypeList;
            }
        }
#if SILVERLIGHT
        private static IsolatedStorageFile _isoFile;
        static IsolatedStorageFile IsoFile
        {
            get
            {
                if (_isoFile == null)
                    _isoFile = System.IO.IsolatedStorage.IsolatedStorageFile.GetUserStoreForApplication();
                return _isoFile;
            }
        }

         public static void SaveMyData(MyDataType sourceData, String targetFileName)
        {
            try
            {
                using (var targetFile = IsoFile.CreateFile(targetFileName))
                {
                    var d = new DataContractSerializer(typeof(MyDataType), KnownTypeList);
                    d.WriteObject(targetFile, sourceData);
                }
            }
            catch (Exception )
            {
                IsoFile.DeleteFile(targetFileName);
            }
        }


        public static MyDataType LoadMyData(string sourceName)
        {
            MyDataType retVal = default(MyDataType);
            if (IsoFile.FileExists(sourceName))
                using (var sourceStream = IsoFile.OpenFile(sourceName, FileMode.Open))
                {
                    var d = new DataContractSerializer(typeof(MyDataType), KnownTypeList);
                    retVal = (MyDataType)d.ReadObject(sourceStream);
                }
            return retVal;
        }
#endif
        public DataSaver()
        {
        }
#if NETFX_CORE
        public static async void SaveMyDataAsync(
            MyDataType sourceData, 
            String targetFileName, 
            Action<MyDataType,String, Exception> OnSaved = null)
        {
            try
            {
                StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(
                    targetFileName, CreationCollisionOption.ReplaceExisting
                    );
                IRandomAccessStream raStream = await file.OpenAsync(FileAccessMode.ReadWrite);
                IOutputStream outStream = raStream.GetOutputStreamAt(0);

                DataContractSerializer serializer = new DataContractSerializer(typeof(MyDataType), KnownTypeList);
                serializer.WriteObject(outStream.AsStreamForWrite(), sourceData);
                await outStream.FlushAsync();
                if(OnSaved!=null)
                    OnSaved(sourceData, targetFileName, null);
            }
            catch (Exception exc)
            {
                if (OnSaved != null)
                {
                    OnSaved(sourceData, targetFileName, exc);
                }
            }
        }

        public static async void LoadDataAsync(string fileName, 
               Action<MyDataType, Exception> loadAction)
        {
            if (loadAction == null)
                return;
            try
            {
                StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(fileName);
                if (file == null) return;
                IInputStream inStream = await file.OpenSequentialReadAsync();

                // Deserialize the Session State. 
                DataContractSerializer serializer = 
                   new DataContractSerializer(typeof(MyDataType), KnownTypeList);
                MyDataType data = (MyDataType)serializer.ReadObject(inStream.AsStreamForRead());
                loadAction(data, null);
            }
            catch (Exception e)
            {
                loadAction(default(MyDataType), e);
            }
        }
#endif

    }
}

许可

本文以及所有相关的源代码和文件均已获得The Code Project Open License (CPOL)的许可。

C# Dev Intermediate Windows-Phone-7 Metro-design 新闻翻译