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.NET core高性能對象轉(zhuǎn)換示例代碼

更新時間：2018年07月10日 10:15:47 作者：costyuan

這篇文章主要給大家介紹了關(guān)于.NET CORE高性能對象轉(zhuǎn)換的相關(guān)資料，文中給出了詳細的示例代碼供大家參考學(xué)習(xí)，需要的朋友可以參考借鑒，下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

前言

NET Core(開放源代碼,跨平臺,x-copy可部署等)有許多令人興奮的方面,其中最值得稱贊的就是其性能了。關(guān)于對象轉(zhuǎn)換已經(jīng)有不少輪子(AutoMapper,TinyMapper) .出于項目需要，手動造一個簡單輪子。下面話不多說了，來一起看看詳細的介紹吧。

示例代碼

g>1.采用靜態(tài)泛型類緩存，避免了拆箱裝箱操作。

2.對于轉(zhuǎn)換對象中有，字段名一樣但是類型不一樣的類時仍可以用

public static class Mapper<TSource, TTarget> where TSource : class where TTarget : class
 {
  public readonly static Func<TSource, TTarget> Map;

  static Mapper()
  {
   if (Map == null)
    Map = GetMap();
  }

  private static Func<TSource, TTarget> GetMap()
  {
   var sourceType = typeof(TSource);
   var targetType = typeof(TTarget);

   var parameterExpression = Expression.Parameter(sourceType, "p");
   var memberInitExpression = GetExpression(parameterExpression, sourceType, targetType);

   var lambda = Expression.Lambda<Func<TSource, TTarget>>(memberInitExpression, parameterExpression);
   return lambda.Compile();
  }

  /// <summary>
  /// 根據(jù)轉(zhuǎn)換源和目標(biāo)獲取表達式樹
  /// </summary>
  /// <param name="parameterExpression">表達式參數(shù)p</param>
  /// <param name="sourceType">轉(zhuǎn)換源類型</param>
  /// <param name="targetType">轉(zhuǎn)換目標(biāo)類型</param>
  /// <returns></returns>
  private static MemberInitExpression GetExpression(Expression parameterExpression, Type sourceType, Type targetType)
  {
   var memberBindings = new List<MemberBinding>();
   foreach (var targetItem in targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite))
   {
    var sourceItem = sourceType.GetProperty(targetItem.Name);

    //判斷實體的讀寫權(quán)限
    if (sourceItem == null || !sourceItem.CanRead || sourceItem.PropertyType.IsNotPublic)
     continue;

    //標(biāo)注NotMapped特性的屬性忽略轉(zhuǎn)換
    if (sourceItem.GetCustomAttribute<NotMappedAttribute>() != null)
     continue;

    var propertyExpression = Expression.Property(parameterExpression, sourceItem);

    //判斷都是class 且類型不相同時
    if (targetItem.PropertyType.IsClass && sourceItem.PropertyType.IsClass && targetItem.PropertyType != sourceItem.PropertyType)
    {
     if (targetItem.PropertyType != targetType)//防止出現(xiàn)自己引用自己無限遞歸
     {
      var memberInit = GetExpression(propertyExpression, sourceItem.PropertyType, targetItem.PropertyType);
      memberBindings.Add(Expression.Bind(targetItem, memberInit));
      continue;
     }
    }

    if (targetItem.PropertyType != sourceItem.PropertyType)
     continue;

    memberBindings.Add(Expression.Bind(targetItem, propertyExpression));
   }
   return Expression.MemberInit(Expression.New(targetType), memberBindings);
  }
 }

3.調(diào)用方法如下

（1）構(gòu)造樣例類

public class A
{
 public int Id { get; set; }
 public string Name { get; set; }
 public C User { get; set; }
 
 /// <summary>
 /// 標(biāo)注為notmapped特性時，不轉(zhuǎn)換賦值
 /// </summary>
 [System.ComponentModel.DataAnnotations.Schema.NotMapped]
 public D UserA { get; set; }
 
}
 
public class B
{
 public int Id { get; set; }
 public string Name { get; set; }
 public D User { get; set; }<br data-filtered="filtered">
 public D UserA { get; set; }
}
 
public class C
{
 public int Id { get; set; }
 public string Name { get; set; }
}
 
public class D
{
 public int Id { get; set; }
 public string Name { get; set; }
}

(2) 調(diào)用

var a = new A
{
 Id = 1,
 Name = "張三",
 User = new C
 {
  Id = 1,
  Name = "李四"
 }
};<br>
B b = Mapper<A, B>.Map(a);//得到轉(zhuǎn)換結(jié)果

4.性能測試

var length = 10000000;
   var listA = new List<A>();
   for (int i = 0; i < length; i++)
   {
    listA.Add(new A
    {
     Id = i,
     Name = "張三",
     User = new C
     {
      Id = i,
      Name = "李四"
     }
    });
   }

   var sw = Stopwatch.StartNew();
   for (int i = 0; i < length; i++)
   {
    var item = listA[i];
    var b = new B
    {
     Id = item.Id,
     Name = item.Name,
     User = new D
     {
      Id = i,
      Name = "李四",
     }
    };
   }
   sw.Stop();
   Console.WriteLine($"原生的時間:{sw.ElapsedMilliseconds}ms");

   //表達式
   Mapper<A, B>.Map(listA[0]);//預(yù)先編譯緩存
   sw.Restart();
   for (int i = 0; i < length; i++)
   {
    Mapper<A, B>.Map(listA[i]);
   }
   sw.Stop();
   Console.WriteLine($"表達式的時間:{sw.ElapsedMilliseconds}ms");

   //AutoMapper
   AutoMapper.Mapper.Initialize(cfg => cfg.CreateMap<A, B>());
   sw.Restart();
   for (int i = 0; i < length; i++)
   {
    var b = AutoMapper.Mapper.Map<B>(listA[i]);
   }
   sw.Stop();
   Console.WriteLine($"AutoMapper時間:{sw.ElapsedMilliseconds}ms");

   //TinyMapper
   TinyMapper.Bind<A, B>();
   sw.Restart();
   for (int i = 0; i < length; i++)
   {
    var b = TinyMapper.Map<B>(listA[i]);
   }
   sw.Stop();
   Console.WriteLine($"TinyMapper時間:{sw.ElapsedMilliseconds}ms");

   Console.ReadLine();

5. 1000萬數(shù)據(jù)不帶子類集結(jié)果