第一章都是讲泛型的，距离上一篇Effective C#的随笔已经是很久以前的事情了。。。

    今天Item4，讲的是泛型的类型推断功能。东西好不好，都是比较出来了，当然也不是绝对的好或者绝对的不好。

    首先上一段不用泛型的代码。 

   1: public static class XmlPersistenceManager

   2: {

   3:     public static object LoadFromFile(Type typeToLoad, string filePath)

   4:     {

   5:         XmlSerializer factory = new XmlSerializer(typeToLoad);

   6:         if (File.Exists(filePath)) {

   7:             using (TextReader tr = new StreamReader(filePath)) {

   8:                 object rVal = factory.Deserialize(tr);

   9:                 return rVal;

  10:             }

  11:         }

  12:         return default(object);//null

  13:     }

  14:     public static void SaveToFile(string filePath, object obj)

  15:     {

  16:         Type theType = obj.GetType();

  17:         XmlSerializer factory = new XmlSerializer(theType);

  18:         using (var sw = new StreamWriter(filePath, false)) {

  19:             factory.Serialize(sw, obj);

  20:         }

  21:     }

  22: }

   1: public static class XmlPersistenceManager2

   2: {

   3:     private static XmlSerializer factory;

   4:     public static object LoadFromFile(Type typeToLoad, string filePath)

   5:     {

   6:         if (factory == null)

   7:             factory = new XmlSerializer(typeToLoad);

   8:  

   9:         if (File.Exists(filePath)) {

  10:             using (TextReader tr = new StreamReader(filePath)) {

  11:                 object rVal = factory.Deserialize(tr);

  12:                 return rVal;

  13:             }

  14:         }

  15:         return default(object);//null

  16:     }

  17:     public static void SaveToFile(string filePath, object obj)

  18:     {

  19:         Type theType = obj.GetType();

  20:         if (factory == null) factory = new XmlSerializer(theType);

  21:         using (var sw = new StreamWriter(filePath, false)) {

  22:             factory.Serialize(sw, obj);

  23:         }

  24:     }

  25: }

   1: public static class GenericXmlPersistenceManager<T>

   2: {

   3:     private static XmlSerializer factory;

   4:     public static T LoadFromFile(string filePath)

   5:     {

   6:         if (File.Exists(filePath)) {

   7:             using (XmlReader inputStream = XmlReader.Create(filePath)) {

   8:                 if (factory == null) factory = new XmlSerializer(typeof(T));

   9:                 T rVal = (T)factory.Deserialize(inputStream);

  10:                 return rVal;

  11:             }

  12:         }

  13:         return default(T);

  14:     }

  15:     public static void SaveToFile(string filePath, T data)

  16:     {

  17:         using (XmlWriter writer = XmlWriter.Create(filePath)) {

  18:             if (factory == null) factory = new XmlSerializer(typeof(T));

  19:             factory.Serialize(writer, data);

  20:         }

  21:     }

  22: }