本文主要是介绍C# 对象类型映射转换方法总结，表达式树实现高效转换，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

       开发过程中经常会遇到对象类型之间的转换映射，例如Model和ViewModel之间的映射绑定，下面总结几种常见的转换方式。事先准备两个类：
CheckFile 和 CheckFileModel

 	public class CheckFile
    {
        public string Id { get; set; }
        public string FileTitle { get; set; }
        public string Author { get; set; }
        public DateTime? CreatTime;
    }
    
    public class CheckFileModel
    {
        public string Id { get; set; }
        public string FileTitle { get; set; }
        public string Author { get; set; }
        public DateTime? CreatTime;
        public string Source { get; set; }
    }

1. 使用强类型赋值绑定

    
    CheckFile checkFile = new CheckFile
    {
        Id = "123",
        FileTitle = "对象类型转换映射",
        Author = "张三",
        CreatTime = DateTime.Now
    };

	CheckFileModel fileModel = new CheckFileModel
    {
        Id = checkFile.Id,
        FileTitle = checkFile.FileTitle,
        Author = checkFile.Author,
        CreatTime = checkFile.CreatTime
    };

2. 使用泛型+反射

	  /// <summary>
      /// 泛型+反射
      /// </summary>
      /// <typeparam name="TOut"></typeparam>
      /// <typeparam name="TIn"></typeparam>
      /// <param name="objIn"></param>
      /// <returns></returns>
      public static TOut TypeConvert<TOut, TIn>(TIn objIn)
      {
          Type tOut = typeof(TOut);
          Type tIn = typeof(TIn);
          TOut outModel = Activator.CreateInstance<TOut>();

          // 属性赋值
          foreach (var prop in tOut.GetProperties())
          {
              var propInfo = tIn.GetProperty(prop.Name);
              if (propInfo != null)
              {
                  var inValue = propInfo.GetValue(objIn);
                  prop.SetValue(outModel, inValue);
              }
          }

          // 字段赋值
          foreach (var field in tOut.GetFields())
          {
              var fieldInfo = tIn.GetField(field.Name);
              if (fieldInfo != null)
              {
                  var inValue = fieldInfo.GetValue(objIn);
                  field.SetValue(outModel, inValue);
              }
          }
          return outModel;
      }

3. 使用Json序列化转换

      /// <summary>
      /// Json序列化转换
      /// </summary>
      /// <typeparam name="TOut"></typeparam>
      /// <typeparam name="TIn"></typeparam>
      /// <param name="objIn"></param>
      /// <returns></returns>
      public static TOut SerializeConvert<TOut, TIn>(TIn objIn)
      {
          string inString = JsonConvert.SerializeObject(objIn);
          TOut outModel = JsonConvert.DeserializeObject<TOut>(inString);
          return outModel;
      }

4. 使用AutoMapper序列化转换

      /// <summary>
      /// AutoMapper序列化转换
      /// </summary>
      /// <typeparam name="TOut"></typeparam>
      /// <typeparam name="TIn"></typeparam>
      /// <param name="objIn"></param>
      /// <returns></returns>
      public static TOut AutoMapperConvert<TOut, TIn>(TIn objIn)
      {
          // 初始化
          Mapper.Initialize(n => n.CreateMap<TIn, TOut>());

          TOut outModel = Mapper.Map<TIn, TOut>(objIn);
          return outModel;
      }

5. 使用Expression表达式目录树转换

      /// <summary>
      /// Expression表达式目录树转换
      /// </summary>
      /// <typeparam name="TOut"></typeparam>
      /// <typeparam name="TIn"></typeparam>
      /// <param name="objIn"></param>
      /// <returns></returns>
      public static TOut ExpressionConvert<TOut, TIn>(TIn objIn)
      {
          ParameterExpression parameterExpression = Expression.Parameter(typeof(TIn), "p");
          List<MemberBinding> memberBindingList = new List<MemberBinding>();

          // 绑定属性
          PropertyInfo[] outPropertyInfos = typeof(TOut).GetProperties();
          foreach (var prop in outPropertyInfos)
          {
              PropertyInfo inPropertyInfo = typeof(TIn).GetProperty(prop.Name);
              if (inPropertyInfo != null)
              {
                  MemberExpression property = Expression.Property(parameterExpression, inPropertyInfo);
                  MemberBinding memberBinding = Expression.Bind(prop, property);
                  memberBindingList.Add(memberBinding);
              }
          }

          // 绑定字段
          FieldInfo[] outFieldInfos = typeof(TOut).GetFields();
          foreach (var field in outFieldInfos)
          {
              FieldInfo inFieldInfo = typeof(TIn).GetField(field.Name);
              if (inFieldInfo != null)
              {
                  MemberExpression fieldInfo = Expression.Field(parameterExpression, inFieldInfo);
                  MemberBinding memberBinding = Expression.Bind(field, fieldInfo);
                  memberBindingList.Add(memberBinding);
              }
          }

          MemberInitExpression memberInitExpression = Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList.ToArray());
          Expression<Func<TIn, TOut>> lambda = Expression.Lambda<Func<TIn, TOut>>(memberInitExpression, new ParameterExpression[]
          {
              parameterExpression
          });
          Func<TIn, TOut> func = lambda.Compile();
          return func.Invoke(objIn);
      }
	  
	  //----------------------------------------------------------
	  // 等价于构造一个下面的表达式
      Expression<Func<CheckFile, CheckFileModel>> lambda = p => new CheckFileModel
      {
          Id = p.Id,
          FileTitle = p.FileTitle,
          Author = p.Author,
          CreatTime = p.CreatTime
      };
      lambda.Compile().Invoke(checkFile);

表达式目录树介绍

每个矩形框为一个节点（表达式类型），节点有多种类型，对于而这个 a*b+2 的几个节点：

• a,b是参数，类型为ParameterExpression
• +，*，为二元运符，类型为BinaryExpression
• 2为常量，类型为ConstantExpression

	Expression<Func<int, int, int>> exp1 = (a, b) => a * b+2;

	//两个参数
	ParameterExpression a = Expression.Parameter(typeof(int), "a");
	ParameterExpression b = Expression.Parameter(typeof(int), "b"); 
	
	//求积
	BinaryExpression Multi=Expression.Multiply(a,b); 
	
	//常量
	ConstantExpression x2 = Expression.Constant(2); 
	
	//求和
	BinaryExpression Add = Expression.Add(Multi, x2); 
	
	//创建一个表示lambda表达式的对象
	LambdaExpression lexp = Expression.Lambda<Func<int, int, int>>(Add, a, b); 

	//查看表达式
	Console.WriteLine(lexp.ToString());
	
	//简单使用
	Expression<Func<int, int, int>> lexp = Expression.Lambda<Func<int, int, int>>(Add, a, b);
	Func<int, int, int> fun = lexp.Compile();
	Console.WriteLine(fun(3,5));

出处：https://blog.csdn.net/qq_31176861/article/details/86551996

=======================================================================================

C# 高性能对象映射(表达式树实现)

前言

  上篇简单实现了对象映射,针对数组，集合，嵌套类并没有给出实现，这一篇继续完善细节。

开源对象映射类库映射分析

 1.AutoMapper 

   实现原理：主要通过表达式树Api 实现对象映射 

   优点： .net功能最全的对象映射类库。

   缺点：当出现复杂类型和嵌套类型时性能直线下降，甚至不如序列化快

 2.TinyMapper

   实现原理：主要通过Emit 实现对象映射 

   优点：速度非常快。在处理复杂类型和嵌套类型性能也很好

   缺点：相对AutoMapper功能上少一些，Emit的实现方案，在代码阅读和调试上相对比较麻烦，而表达式树直接观察 DebugView中生成的代码结构便可知道问题所在

 3. 本文的对象映射库

  针对AutoMapper 处理复杂类型和嵌套类型时性能非常差的情况，自己实现一个表达式树版的高性能方案

此篇记录下实现对象映射库的过程

  构造测试类

 1     public class TestA
 2     {
 3         public int Id { get; set; }
 4         public string Name { get; set; }
 5 
 6         public TestC TestClass { get; set; }
 7 
 8         public IEnumerable<TestC> TestLists { get; set; }
 9     }
10 
11     public class TestB
12     {
13         public int Id { get; set; }
14         public string Name { get; set; }
15 
16         public TestD TestClass { get; set; }
17 
18         public TestD[] TestLists { get; set; }
19     }
20 
21     public class TestC
22     {
23         public int Id { get; set; }
24         public string Name { get; set; }
25 
26         public TestC SelfClass { get; set; }
27     }
28 
29     public class TestD
30     {
31         public int Id { get; set; }
32         public string Name { get; set; }
33 
34         public TestD SelfClass { get; set; }
35     }

 1.初步实现

    利用表达式树给属性赋值 利用 Expresstion.New构造 var b=new B{};

 1       private static Func<TSource, TTarget> GetMap<TSource, TTarget>()
 2         {
 3             var sourceType = typeof(TSource);
 4             var targetType = typeof(TTarget);
 5 
 6             //构造 p=>
 7             var parameterExpression = Expression.Parameter(sourceType, "p");
 8 
 9             //构造 p=>new TTarget{ Id=p.Id,Name=p.Name };
10             var memberBindingList = new List<MemberBinding>();
11             foreach (var sourceItem in sourceType.GetProperties())
12             {
13                 var targetItem = targetType.GetProperty(sourceItem.Name);
14                 if (targetItem == null || sourceItem.PropertyType != targetItem.PropertyType)
15                     continue;
16 
17                 var property = Expression.Property(parameterExpression, sourceItem);
18                 var memberBinding = Expression.Bind(targetItem, property);
19                 memberBindingList.Add(memberBinding);
20             }
21             var memberInitExpression = Expression.MemberInit(Expression.New(targetType), memberBindingList);
22 
23             var lambda = Expression.Lambda<Func<TSource, TTarget>>(memberInitExpression, parameterExpression );
24 
25             Console.WriteLine(lambda);
26             return lambda.Compile();
27         }

  调用如下

14 
15     class Program
16     {
17         static void Main(string[] args)
18         {
19             var testA = new TestA { Id = 1, Name = "张三" };
20             var func = Map<TestA, TestB>();
21             TestB testB = func(testA);
22             Console.WriteLine($"testB.Id={testB.Id},testB.Name={testB.Name}");
23             Console.ReadLine();
24         }
25     }

  输出结果

总结：此方法需要调用前需要手动编译下，然后再调用委托没有缓存委托，相对麻烦。

2.缓存实现

   利用静态泛型类缓存泛型委托

 1     public class DataMapper<TSource, TTarget>
 2     {
 3         private static Func<TSource, TTarget> MapFunc { get; set; }
 4 
 5         public static TTarget Map(TSource source)
 6         {
 7             if (MapFunc == null)
 8                 MapFunc = GetMap();//方法在上边
 9             return MapFunc(source);
10         }11    }

   调用方法

1         static void Main(string[] args)
2         {
3             var testA = new TestA { Id = 1, Name = "张三" };
4             TestB testB = DataMapper<TestA, TestB>.Map(testA);//委托不存在时自动生成，存在时调用静态缓存
5 
6             Console.WriteLine($"testB.Id={testB.Id},testB.Name={testB.Name}");
7             Console.ReadLine();
8         }

   输出结果

  总结：引入静态泛型类能解决泛型委托缓存提高性能，但是有两个问题  1.当传入参数为null时 则会抛出空引用异常 2.出现复杂类型上述方法便不能满足了

3.解决参数为空值和复杂类型的问题

    首先先用常规代码实现下带有复杂类型赋值的情况

 1 public TestB GetTestB(TestA testA)
 2         {
 3             TestB testB;
 4             if (testA != null)
 5             {
 6                 testB = new TestB();
 7                 testB.Id = testA.Id;
 8                 testB.Name = testA.Name;
 9                 if (testA.TestClass != null)
10                 {
11                     testB.TestClass = new TestD();
12                     testB.TestClass.Id = testA.TestClass.Id;
13                     testB.TestClass.Name = testA.TestClass.Name;
14                 }
15             }
16             else
17             {
18                 testB = null;
19             }
20             return testB;
21         }

  将上面的代码翻译成表达式树

 1         private static Func<TSource, TTarget> GetMap()
 2         {
 3             var sourceType = typeof(TSource);
 4             var targetType = typeof(TTarget);
 5 
 6             //Func委托传入变量
 7             var parameter = Expression.Parameter(sourceType);
 8 
 9             //声明一个返回值变量
10             var variable = Expression.Variable(targetType);
11             //创建一个if条件表达式
12             var test = Expression.NotEqual(parameter, Expression.Constant(null, sourceType));// p==null;
13             var ifTrue = Expression.Block(GetExpression(parameter, variable, sourceType, targetType));
14             var IfThen = Expression.IfThen(test, ifTrue);
15 
16             //构造代码块 
17             var block = Expression.Block(new[] { variable }, parameter, IfThen, variable);
18 
19             var lambda = Expression.Lambda<Func<TSource, TTarget>>(block, parameter);
20             return lambda.Compile();
21         }
22 
23         private static List<Expression> GetExpression(Expression parameter, Expression variable, Type sourceType, Type targetType)
24         {
25             //创建一个表达式集合
26             var expressions = new List<Expression>();
27 
28             expressions.Add(Expression.Assign(variable, Expression.MemberInit(Expression.New(targetType))));
29 
30             foreach (var targetItem in targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite))
31             {
32                 var sourceItem = sourceType.GetProperty(targetItem.Name);
33 
34                 //判断实体的读写权限
35                 if (sourceItem == null || !sourceItem.CanRead || sourceItem.PropertyType.IsNotPublic)
36                     continue;
37 
38                 var sourceProperty = Expression.Property(parameter, sourceItem);
39                 var targetProperty = Expression.Property(variable, targetItem);
40 
41                 //判断都是class 且类型不相同时
42                 if (targetItem.PropertyType.IsClass && sourceItem.PropertyType.IsClass && targetItem.PropertyType != sourceItem.PropertyType)
43                 {
44                     if (targetItem.PropertyType != targetType)//不处理嵌套循环的情况
45                     {
46                         //由于类型是class 所以默认值是null
47                         var testItem = Expression.NotEqual(sourceProperty, Expression.Constant(null, sourceItem.PropertyType));
48 
49                         var itemExpressions = GetExpression(sourceProperty, targetProperty, sourceItem.PropertyType, targetItem.PropertyType);
50                         var ifTrueItem = Expression.Block(itemExpressions);
51 
52                         var IfThenItem = Expression.IfThen(testItem, ifTrueItem);
53                         expressions.Add(IfThenItem);
54 
55                         continue;
56                     }
57                 }
58 
59                 //目标值类型时 且两者类型不一致时跳过
60                 if (targetItem.PropertyType != sourceItem.PropertyType)
61                     continue;
62 
63                 expressions.Add(Expression.Assign(targetProperty, sourceProperty));
64             }
65 
66             return expressions;
67         }

总结：此方案，运用 Expression.IfThen(testItem, ifTrueItem) 判断空值问题，通过递归调用 GetExpression()方法，处理复杂类型。 但是。。。针对嵌套类仍然不能解决。因为表达式树是在实际调用方法之前就生成的，在没有实际的

           参数值传入之前，生成的表达式是不知道有多少层级的。有个比较low的方案是，预先设定嵌套层级为10层，然后生成一个有10层 if(P!=null) 的判断。如果传入的参数层级超过10层了呢，就得手动调整生成的树，此方案也否决。

           最后得出的结论只能在表达式中动态调用方法。

4.最终版本

   通过动态调用方法解决嵌套类，代码如下

  using static System.Linq.Expressions.Expression;
    public static class Mapper<TSource, TTarget> where TSource : class where TTarget : class
    {
public readonly static Func<TSource, TTarget> MapFunc = GetMapFunc();

public readonly static Action<TSource, TTarget> MapAction = GetMapAction();

/// <summary>
/// 将对象TSource转换为TTarget
/// </summary>
/// <param name="source"></param>
/// <returns></returns>
public static TTarget Map(TSource source) => MapFunc(source);

public static List<TTarget> MapList(IEnumerable<TSource> sources)=> sources.Select(MapFunc).ToList();



/// <summary>
/// 将对象TSource的值赋给给TTarget
/// </summary>
/// <param name="source"></param>
/// <param name="target"></param>
public static void Map(TSource source, TTarget target) => MapAction(source, target);

private static Func<TSource, TTarget> GetMapFunc()
        {
            var sourceType = typeof(TSource);
            var targetType = typeof(TTarget);
            //Func委托传入变量
            var parameter = Parameter(sourceType, "p");

            var memberBindings = new List<MemberBinding>();
            var targetTypes = targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite);
            foreach (var targetItem in targetTypes)
            {
                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 sourceProperty = Property(parameter, sourceItem);

                //当非值类型且类型不相同时
                if (!sourceItem.PropertyType.IsValueType && sourceItem.PropertyType != targetItem.PropertyType)
                {
                    //判断都是(非泛型)class
                    if (sourceItem.PropertyType.IsClass && targetItem.PropertyType.IsClass &&
                        !sourceItem.PropertyType.IsGenericType && !targetItem.PropertyType.IsGenericType)
                    {
                        var expression = GetClassExpression(sourceProperty, sourceItem.PropertyType, targetItem.PropertyType);
                        memberBindings.Add(Bind(targetItem, expression));
                    }

                    //集合数组类型的转换
                    if (typeof(IEnumerable).IsAssignableFrom(sourceItem.PropertyType) && typeof(IEnumerable).IsAssignableFrom(targetItem.PropertyType))
                    {
                        var expression = GetListExpression(sourceProperty, sourceItem.PropertyType, targetItem.PropertyType);
                        memberBindings.Add(Bind(targetItem, expression));
                    }

                    continue;
                }

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

                memberBindings.Add(Bind(targetItem, sourceProperty));
            }

            //创建一个if条件表达式
            var test = NotEqual(parameter, Constant(null, sourceType));// p==null;
            var ifTrue = MemberInit(New(targetType), memberBindings);
            var condition = Condition(test, ifTrue, Constant(null, targetType));

            var lambda = Lambda<Func<TSource, TTarget>>(condition, parameter);
            return lambda.Compile();
        }

        /// <summary>
        /// 类型是clas时赋值
        /// </summary>
        /// <param name="sourceProperty"></param>
        /// <param name="targetProperty"></param>
        /// <param name="sourceType"></param>
        /// <param name="targetType"></param>
        /// <returns></returns>
        private static Expression GetClassExpression(Expression sourceProperty, Type sourceType, Type targetType)
        {
            //条件p.Item!=null    
            var testItem = NotEqual(sourceProperty, Constant(null, sourceType));

            //构造回调 Mapper<TSource, TTarget>.Map()
            var mapperType = typeof(Mapper<,>).MakeGenericType(sourceType, targetType);
            var iftrue = Call(mapperType.GetMethod(nameof(Map), new[] { sourceType }), sourceProperty);

            var conditionItem = Condition(testItem, iftrue, Constant(null, targetType));

            return conditionItem;
        }

        /// <summary>
        /// 类型为集合时赋值
        /// </summary>
        /// <param name="sourceProperty"></param>
        /// <param name="targetProperty"></param>
        /// <param name="sourceType"></param>
        /// <param name="targetType"></param>
        /// <returns></returns>
        private static Expression GetListExpression(Expression sourceProperty, Type sourceType, Type targetType)
        {
            //条件p.Item!=null    
            var testItem = NotEqual(sourceProperty, Constant(null, sourceType));

            //构造回调 Mapper<TSource, TTarget>.MapList()
            var sourceArg = sourceType.IsArray ? sourceType.GetElementType() : sourceType.GetGenericArguments()[0];
            var targetArg = targetType.IsArray ? targetType.GetElementType() : targetType.GetGenericArguments()[0];
            var mapperType = typeof(Mapper<,>).MakeGenericType(sourceArg, targetArg);

            var mapperExecMap = Call(mapperType.GetMethod(nameof(MapList), new[] { sourceType }), sourceProperty);

            Expression iftrue;
            if (targetType == mapperExecMap.Type)
            {
                iftrue = mapperExecMap;
            }
            else if (targetType.IsArray)//数组类型调用ToArray()方法
            {
                iftrue = Call(mapperExecMap, mapperExecMap.Type.GetMethod("ToArray"));
            }
            else if (typeof(IDictionary).IsAssignableFrom(targetType))
            {
                iftrue = Constant(null, targetType);//字典类型不转换
            }
            else
            {
                iftrue = Convert(mapperExecMap, targetType);
            }

            var conditionItem = Condition(testItem, iftrue, Constant(null, targetType));

            return conditionItem;
        }

        private static Action<TSource, TTarget> GetMapAction()
        {
            var sourceType = typeof(TSource);
            var targetType = typeof(TTarget);
            //Func委托传入变量
            var sourceParameter = Parameter(sourceType, "p");

            var targetParameter = Parameter(targetType, "t");

            //创建一个表达式集合
            var expressions = new List<Expression>();

            var targetTypes = targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite);
            foreach (var targetItem in targetTypes)
            {
                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 sourceProperty = Property(sourceParameter, sourceItem);
                var targetProperty = Property(targetParameter, targetItem);

                //当非值类型且类型不相同时
                if (!sourceItem.PropertyType.IsValueType && sourceItem.PropertyType != targetItem.PropertyType)
                {
                    //判断都是(非泛型)class
                    if (sourceItem.PropertyType.IsClass && targetItem.PropertyType.IsClass &&
                        !sourceItem.PropertyType.IsGenericType && !targetItem.PropertyType.IsGenericType)
                    {
                        var expression = GetClassExpression(sourceProperty, sourceItem.PropertyType, targetItem.PropertyType);
                        expressions.Add(Assign(targetProperty, expression));
                    }

                    //集合数组类型的转换
                    if (typeof(IEnumerable).IsAssignableFrom(sourceItem.PropertyType) && typeof(IEnumerable).IsAssignableFrom(targetItem.PropertyType))
                    {
                        var expression = GetListExpression(sourceProperty, sourceItem.PropertyType, targetItem.PropertyType);
                        expressions.Add(Assign(targetProperty, expression));
                    }

                    continue;
                }

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


                expressions.Add(Assign(targetProperty, sourceProperty));
            }

            //当Target!=null判断source是否为空
            var testSource = NotEqual(sourceParameter, Constant(null, sourceType));
            var ifTrueSource = Block(expressions);
            var conditionSource = IfThen(testSource, ifTrueSource);

            //判断target是否为空
            var testTarget = NotEqual(targetParameter, Constant(null, targetType));
            var conditionTarget = IfThen(testTarget, conditionSource);

            var lambda = Lambda<Action<TSource, TTarget>>(conditionTarget, sourceParameter, targetParameter);
            return lambda.Compile();
        }
    }

输出的 表达式

格式化后

 1 p => IIF((p != null), 
 2      new TestB() 
 3      {
 4        Id = p.Id, 
 5        Name = p.Name, 
 6        TestClass = IIF(
 7                    (p.TestClass != null),
 8                     Map(p.TestClass),
 9                     null
10                     ),
11        TestLists = IIF(
12                      (p.TestLists != null),
13                       MapList(p.TestLists).ToArray(),
14                       null
15                      )
16        },
17        null)

说明 Map(p.TestClass)   MapList(p.TestLists).ToArray(),  完整的信息为 Mapper<TestC,TestD>.Map()   Mapper<TestC,TestD>.MapList()  

   总结：解决嵌套类的核心代码

101             //构造回调 Mapper<TSource, TTarget>.Map()
102             var mapperType = typeof(DataMapper<,>).MakeGenericType(sourceType, targetType);
103             var mapperExecMap = Expression.Call(mapperType.GetMethod(nameof(Map), new[] { sourceType }), sourceProperty);

   利用Expression.Call  根据参数类型动态生成 对象映射的表达式

性能测试

   写了这么多最终目的还是为了解决性能问题，下面将对比下性能

  1.测试类

  1     public static class MapperTest
  2     {
  3         //执行次数
  4         public static int Count = 100000;
  5 
  6         //简单类型
  7         public static void Nomal()
  8         {
  9             Console.WriteLine($"******************简单类型:{Count / 10000}万次执行时间*****************");
 10             var model = new TestA
 11             {
 12                 Id =1,
 13                 Name = "张三",
 14             };
 15 
 16             //计时
 17             var sw = Stopwatch.StartNew();
 18             for (int i = 0; i < Count; i++)
 19             {
 20                 if (model != null)
 21                 {
 22                     var b = new TestB
 23                     {
 24                         Id = model.Id,
 25                         Name = model.Name,
 26                     };
 27                 }
 28             }
 29             sw.Stop();
 30             Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");
 31 
 32             Exec(model);
 33         }
 34 
 35         //复杂类型
 36         public static void Complex()
 37         {
 38             Console.WriteLine($"********************复杂类型:{Count / 10000}万次执行时间*********************");
 39             var model = new TestA
 40             {
 41                 Id = 1,
 42                 Name = "张三",
 43                 TestClass = new TestC
 44                 {
 45                     Id = 2,
 46                     Name = "lisi",
 47                 },
 48             };
 49 
 50             //计时
 51             var sw = Stopwatch.StartNew();
 52             for (int i = 0; i < Count; i++)
 53             {
 54 
 55                 if (model != null)
 56                 {
 57                     var b = new TestB
 58                     {
 59                         Id = model.Id,
 60                         Name = model.Name,
 61                     };
 62                     if (model.TestClass != null)
 63                     {
 64                         b.TestClass = new TestD
 65                         {
 66                             Id = i,
 67                             Name = "lisi",
 68                         };
 69                     }
 70                 }
 71             }
 72             sw.Stop();
 73             Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");
 74             Exec(model);
 75         }
 76 
 77         //嵌套类型
 78         public static void Nest()
 79         {
 80             Console.WriteLine($"*****************嵌套类型:{Count / 10000}万次执行时间*************************");
 81             var model = new TestA
 82             {
 83                 Id = 1,
 84                 Name = "张三",
 85                 TestClass = new TestC
 86                 {
 87                     Id = 1,
 88                     Name = "lisi",
 89                     SelfClass = new TestC
 90                     {
 91                         Id = 2,
 92                         Name = "lisi",
 93                         SelfClass = new TestC
 94                         {
 95                             Id = 3,
 96                             Name = "lisi",
 97                             SelfClass = new TestC
 98                             {
 99                                 Id = 4,
100                                 Name = "lisi",
101                             },
102                         },
103                     },
104                 },
105             };
106             //计时
107             var item = model;
108             var sw = Stopwatch.StartNew();
109             for (int i = 0; i < Count; i++)
110             {
111                 //这里每一步需要做非空判断的，书写太麻烦省去了
112                 if (model != null)
113                 {
114                     var b = new TestB
115                     {
116                         Id = model.Id,
117                         Name = model.Name,
118                         TestClass = new TestD
119                         {
120                             Id = model.TestClass.Id,
121                             Name = model.TestClass.Name,
122                             SelfClass = new TestD
123                             {
124                                 Id = model.TestClass.SelfClass.Id,
125                                 Name = model.TestClass.SelfClass.Name,
126                                 SelfClass = new TestD
127                                 {
128                                     Id = model.TestClass.SelfClass.SelfClass.Id,
129                                     Name = model.TestClass.SelfClass.SelfClass.Name,
130                                     SelfClass = new TestD
131                                     {
132                                         Id = model.TestClass.SelfClass.SelfClass.SelfClass.Id,
133                                         Name = model.TestClass.SelfClass.SelfClass.SelfClass.Name,
134                                     },
135                                 },
136                             },
137                         },
138                     };
139                 }
140             }
141             sw.Stop();
142             Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");
143 
144             Exec(model);
145         }
146 
147         //集合
148         public static void List()
149         {
150             Console.WriteLine($"********************集合类型:{Count/10000}万次执行时间***************************");
151 
152             var model = new TestA
153             {
154                 Id = 1,
155                 Name = "张三",
156                 TestLists = new List<TestC> {
157                             new TestC{
158                              Id = 1,
159                             Name =  "张三",
160                            },
161                             new TestC{
162                             Id = -1,
163                             Name =  "张三",
164                            },
165                         }
166             };
167 
168 
169             //计时
170             var sw = Stopwatch.StartNew();
171             for (int i = 0; i < Count; i++)
172             {
173                 var item = model;
174                 if (item != null)
175                 {
176                     var b = new TestB
177                     {
178                         Id = item.Id,
179                         Name = item.Name,
180                         TestLists = new List<TestD> {
181                             new TestD{
182                                    Id = item.Id,
183                             Name = item.Name,
184                            },
185                             new TestD{
186                             Id = -item.Id,
187                             Name = item.Name,
188                            },
189                         }.ToArray()
190                     };
191                 }
192             }
193             sw.Stop();
194             Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");
195 
196             Exec(model);
197         }
198 
199         public static void Exec(TestA model)
200         {
201             //表达式
202             Mapper<TestA, TestB>.Map(model);
203             var sw = Stopwatch.StartNew();
204             for (int i = 0; i < Count; i++)
205             {
206                 var b = Mapper<TestA, TestB>.Map(model);
207             }
208             sw.Stop();
209             Console.WriteLine($"表达式的时间:{sw.ElapsedMilliseconds}ms");
210 
211             //AutoMapper
212             sw.Restart();
213             for (int i = 0; i < Count; i++)
214             {
215                 var b = AutoMapper.Mapper.Map<TestA, TestB>(model);
216             }
217             sw.Stop();
218             Console.WriteLine($"AutoMapper时间:{sw.ElapsedMilliseconds}ms");
219 
220             //TinyMapper
221             sw.Restart();
222             for (int i = 0; i < Count; i++)
223             {
224                 var b = TinyMapper.Map<TestA, TestB>(model);
225             }
226             sw.Stop();
227             Console.WriteLine($"TinyMapper时间:{sw.ElapsedMilliseconds}ms");
228         }
229     }
230 
231 

2.调用测试

 1         static void Main(string[] args)
 2         {
 3             AutoMapper.Mapper.Initialize(cfg => cfg.CreateMap<TestA, TestB>());
 4             TinyMapper.Bind<TestA, TestB>();
 5             Mapper<TestA, TestB>.Map(new TestA());
 6 
 7 
 8             MapperTest.Count = 10000;
 9             MapperTest.Nomal();
10             MapperTest.Complex();
11             MapperTest.Nest();
12             MapperTest.List();
13 
14             MapperTest.Count = 100000;
15             MapperTest.Nomal();
16             MapperTest.Complex();
17             MapperTest.Nest();
18             MapperTest.List();
19 
20             MapperTest.Count = 1000000;
21             MapperTest.Nomal();
22             MapperTest.Complex();
23             MapperTest.Nest();
24             MapperTest.List();
25 
26             MapperTest.Count = 10000000;
27             MapperTest.Nomal();
28             MapperTest.Complex();
29             MapperTest.Nest();
30             MapperTest.List();
31 
32 
33             Console.WriteLine($"------------结束--------------------");
34             Console.ReadLine();
35         }

3.结果

1万次

10万次

100万次

1000万次

上图结果AutoMapper 在非简单类型的转换上比其他方案有50倍以上的差距，几乎就跟反射的结果一样。

作者：costyuan

GitHub地址：https://github.com/bieyuan/.net-core-DTO

出处：https://www.cnblogs.com/castyuan/p/9324088.html

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