.NET core高性能对象转换示例代码

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>  /// 根据转换源和目标获取表达式树  /// </summary>  /// <param name="parameterExpression">表达式参数p</param>  /// <param name="sourceType">转换源类型</param>  /// <param name="targetType">转换目标类型</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);    //判断实体的读写权限    if (sourceItem == null || !sourceItem.CanRead || sourceItem.PropertyType.IsNotPublic)     continue;    //标注NotMapped特性的属性忽略转换    if (sourceItem.GetCustomAttribute<NotMappedAttribute>() != null)     continue;    var propertyExpression = Expression.Property(parameterExpression, sourceItem);    //判断都是class 且类型不相同时    if (targetItem.PropertyType.IsClass && sourceItem.PropertyType.IsClass && targetItem.PropertyType != sourceItem.PropertyType)    {     if (targetItem.PropertyType != targetType)//防止出现自己引用自己无限递归     {      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);  } }

public class A{ public int Id { get; set; } public string Name { get; set; } public C User { get; set; }  /// <summary> /// 标注为notmapped特性时，不转换赋值 /// </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; }}

var a = new A{ Id = 1, Name = "张三", User = new C {  Id = 1,  Name = "李四" }};<br>B b = Mapper<A, B>.Map(a);//得到转换结果

var length = 10000000;   var listA = new List<A>();   for (int i = 0; i < length; i++)   {    listA.Add(new A    {     Id = i,     Name = "张三",     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($"原生的时间:{sw.ElapsedMilliseconds}ms");   //表达式   Mapper<A, B>.Map(listA[0]);//预先编译缓存   sw.Restart();   for (int i = 0; i < length; i++)   {    Mapper<A, B>.Map(listA[i]);   }   sw.Stop();   Console.WriteLine($"表达式的时间:{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($"AutoMapper时间:{sw.ElapsedMilliseconds}ms");   //TinyMapper   TinyMapper.Bind<A, B>();   sw.Restart();   for (int i = 0; i < length; i++)   {    var b = TinyMapper.Map<B>(listA[i]);   }   sw.Stop();   Console.WriteLine($"TinyMapper时间:{sw.ElapsedMilliseconds}ms");   Console.ReadLine();