.NET core高性能对象转换示例代码_实用技巧_

 public static class Mapper where TSource : class where TTarget : class { public readonly static Func Map; static Mapper() { if (Map == null) Map = GetMap(); } private static Func 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>(memberInitExpression, parameterExpression); return lambda.Compile(); } /// 
 /// 根据转换源和目标获取表达式树 /// 
 /// 表达式参数p /// 转换源类型 /// 转换目标类型 ///  private static MemberInitExpression GetExpression(Expression parameterExpression, Type sourceType, Type targetType) { var memberBindings = new List(); 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() != 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; } /// 
 /// 标注为notmapped特性时，不转换赋值 /// 
 [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; }
 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" } };
 B b = Mapper.Map(a);//得到转换结果

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