C# - 將 Object 的 Property 與 Value 轉換為 Dictionary

之前筆記使用 C# 存取 InfluxDB 提到正在嘗試導入 InfluxDB，POC 使用到的 library - InfluxData.Net 在儲存資料時僅接受 Dictionary，如果需要將整個 c# object 儲存起來就必需做轉換，考量到專案規劃用量大，因此希望能儘量降低無謂地效能損耗，所以特別針對 c# object 的 Property 與 Value 轉型為 Dictionary 幾種方式的效能進行比較測試

我個人才疏學淺絕對是找不到最佳解，我就先紀錄一下測試的情境與方式，相信強大的同事們一定會幫忙找出更好的解法

基本環境說明

macOS Mojave 10.14.6
.NET Core SDK 2.2.301 (.NET Core Runtime 2.2.6)
NuGet package
- BenchmarkDotNet 0.11.5
- Bogus 28.3.1

測試用基礎程式碼

User.cs

public class User
{
    public Guid UserId { get; set; }
    public string Name { get; set; }
    public DateTime Birthday { get; set; }
    public decimal CurrentSalary { get; set; }
}

轉換的備選方式

使用 Reflection

public List<IDictionary<string, object>> ByReflection()
{
    var h = 0;
    var result= new List<IDictionary<string, object>>();
    for (var i = 0; i < N; i++)
    {
       var dict=_user.GetType().GetProperties().ToDictionary(x => x.Name, x => x.GetValue(_user, null));
        h = $"{h}{dict.GetHashCode()}".GetHashCode();
        result.Add(dict);
    }

    return result;
}

使用TypeDescriptor

public List<IDictionary<string, object>> ByTypeDescriptor()
{
    var result= new List<IDictionary<string, object>>();

    var h = 0;
    for (var i = 0; i < N; i++)
    {
        var dict=_user.TypeDescriptorToDictionary();
        h = $"{h}{dict.GetHashCode()}".GetHashCode();
        result.Add(dict);
    }
    return result;
}

extension method

public static class ObjectToDictionaryHelper
{
    public static IDictionary<string, object> TypeDescriptorToDictionary(this object source)
    {
        return source.TypeDescriptorToDictionary<object>();
    }

    public static IDictionary<string, T> TypeDescriptorToDictionary<T>(this object source)
    {
        if (source == null) ThrowExceptionWhenSourceArgumentIsNull();

        var dictionary = new Dictionary<string, T>();
        foreach (PropertyDescriptor property in TypeDescriptor.GetProperties(source))
        {
            object value = property.GetValue(source);
            if (IsOfType<T>(value))
            {
                dictionary.Add(property.Name, (T)value);
            }
        }
        return dictionary;
    }

    private static bool IsOfType<T>(object value)
    {
        return value is T;
    }

    private static void ThrowExceptionWhenSourceArgumentIsNull()
    {
        throw new NullReferenceException("Unable to convert anonymous object to a dictionary. The source anonymous object is null.");
    }
}

使用 Expression

public List<IDictionary<string, object>> ByPocoToDictionary()
{
    var result= new List<IDictionary<string, object>>();

    var h = 0;
    for (var i = 0; i < N; i++)
    {
        var dict=_user.ExpressionToDictionary();
        h = $"{h}{dict.GetHashCode()}".GetHashCode();
       result.Add(dict);
    }
    return result;
}

extension method

public static class PocoToDictionary
{
    private static readonly MethodInfo AddToDictionaryMethod = typeof(IDictionary<string, object>).GetMethod("Add");
    private static readonly ConcurrentDictionary<Type, Func<object, IDictionary<string, object>>> Converters = new ConcurrentDictionary<Type, Func<object,  IDictionary<string, object>>>();
    private static readonly ConstructorInfo DictionaryConstructor = typeof(Dictionary<string, object>).GetConstructors().FirstOrDefault(c => c.IsPublic &&  !c.GetParameters().Any());

    public static IDictionary<string, object> ExpressionToDictionary(this object obj) => obj == null ? null : Converters.GetOrAdd(obj.GetType(), o =>
    {
        var outputType = typeof(IDictionary<string, object>);
        var inputType = obj.GetType();
        var inputExpression = Expression.Parameter(typeof(object), "input");
        var typedInputExpression = Expression.Convert(inputExpression, inputType);
        var outputVariable = Expression.Variable(outputType, "output");
        var returnTarget = Expression.Label(outputType);
        var body = new List<Expression>
        {
            Expression.Assign(outputVariable, Expression.New(DictionaryConstructor))
        };
        body.AddRange(
            from prop in inputType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.FlattenHierarchy)
            where prop.CanRead && (prop.PropertyType.IsPrimitive || prop.PropertyType == typeof(string))
            let getExpression = Expression.Property(typedInputExpression, prop.GetMethod)
            select Expression.Call(outputVariable, AddToDictionaryMethod, Expression.Constant(prop.Name), getExpression));
        body.Add(Expression.Return(returnTarget, outputVariable));
        body.Add(Expression.Label(returnTarget, Expression.Constant(null, outputType)));

        var lambdaExpression = Expression.Lambda<Func<object, IDictionary<string, object>>>(
            Expression.Block(new[] { outputVariable }, body),
            inputExpression);

        return lambdaExpression.Compile();
    })(obj);
}

實際測試程式

測試用 class

 public class ObjectToDictionary
{
    private const int N = 1000000;
    private readonly User _user;
        
    public ObjectToDictionary()
    {
      _user= new Faker<User>()
          .RuleFor(a => a.UserId, f => f.Random.Guid())
          .RuleFor(a => a.Name, f => f.Name.FirstName())
          .RuleFor(a => a.Birthday, f => f.Date.Past())
          .RuleFor(a => a.CurrentSalary, f => f.Random.Decimal(0M, 10000M))
          .Generate();

    }

    [Benchmark]
    public List<IDictionary<string, object>> ByReflection()
    {
        var h = 0;
        var result= new List<IDictionary<string, object>>();
        for (var i = 0; i < N; i++)
        {
           var dict=_user.GetType().GetProperties().ToDictionary(x => x.Name, x => x.GetValue(_user, null));
            h = $"{h}{dict.GetHashCode()}".GetHashCode();
            result.Add(dict);
        }

        return result;
    }

    [Benchmark]
    public List<IDictionary<string, object>> ByExpression()
    {
        var result= new List<IDictionary<string, object>>();

        var h = 0;
        for (var i = 0; i < N; i++)
        {
            var dict=_user.ExpressionToDictionary();
            h = $"{h}{dict.GetHashCode()}".GetHashCode();
           result.Add(dict);
        }
        return result;
    }
        
    [Benchmark]
    public List<IDictionary<string, object>> ByTypeDescriptor()
    {
        var result= new List<IDictionary<string, object>>();

        var h = 0;
        for (var i = 0; i < N; i++)
        {
            var dict=_user.TypeDescriptorToDictionary();
            h = $"{h}{dict.GetHashCode()}".GetHashCode();
            result.Add(dict);
        }
        return result;
    }
}

執行測試

 var summary = BenchmarkRunner.Run<ObjectToDictionary>();

效能數據

Method	Mean	Error	StdDev
ByReflection	5.017 s	0.3736 s	1.0957 s
ByExpression	1.733 s	0.0365 s	0.0838 s
ByTypeDescriptor	7.087 s	0.1385 s	0.2982 s

心得

還沒執行效能測試前就猜測應該會是 expression 勝出，雖然也想過使用 emit，但誠如忠成老師 C# 快速動態建立物件實體技巧提到的可讀性，加上我也不確定 emit 寫出來後自己可以記得多久，想想還是別找自己麻煩了XD，不過如果之後有多些時間，也會做個 emit 版本的效能比較，畢竟量大的情境下任何一點效能提升都會有幫助，對系統也都是正面的

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