具有字典属性的 C# 匿名对象

Question

我正在尝试将字典转换为匿名类型，每个键都有一个属性。

我尝试用谷歌搜索，但我只能找到如何将匿名对象转换为字典。

我的字典看起来像这样：

var dict = new Dictionary<string, string>
{
    {"Id", "1"},
    {"Title", "My title"},
    {"Description", "Blah blah blah"},
};

我想返回一个看起来像这样的匿名对象。

var o = new 
{
    Id = "1",
    Title = "My title",
    Description = "Blah blah blah"
};

所以我希望它遍历字典中的每个 keyValuePair 并在对象中为每个键创建一个属性。

我不知道从哪里开始。

请帮忙。

Answer 1

你不能，基本上。匿名类型由编译器创建，因此它们存在于您的程序集中，其中包含所有属性名称。 （在这种情况下，属性 types 不是问题 - 作为实现细节，编译器会创建一个泛型类型，然后使用适当的类型参数创建该类型的实例。）

您要求的类型具有在 执行 时确定的属性 - 这与匿名类型的工作方式不符。您基本上必须在执行时使用它来编译代码 - 这会很痛苦，因为它会在不同的程序集中，并且匿名类型是内部的......

也许您应该改用ExpandoObject？然后任何使用dynamic 的东西都可以正常访问属性。

Answer 2

以下是作为ExpandoObject 的方法（来自this post 的帮助）

var dict = new Dictionary<string, string>
{
    {"Id", "1"},
    {"Title", "My title"},
    {"Description", "Blah blah blah"},
};

var expando = new ExpandoObject()  as IDictionary<string, Object>;
foreach(var kvp in dict)
    expando.Add(kvp.Key, kvp.Value);

Answer 3

基本上，这不是您可以轻易做到的事情；匿名类型仍然拥有所有常见的幕后代码：只是你看不到它。您可以通过dynamic 做同样的事情，但这不适用于期望反射等的API - 因此，对于大多数代码字典，您必须按键访问访问会比匿名类型或dynamic 类型更方便。

Answer 4

它不是匿名对象，但您可以使用DynamicObject 来完成此操作！您可以执行以下操作。

public class MyExpando : DynamicObject
{
    Dictionary<string, object> dictionary;
    public MyExpando()
    {
       dictionary = new Dictionary<string, object>
       {
            {"Id", "1"},
            {"Title", "My title"},
            {"Description", "Blah blah blah"},
       };
    }

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        return dictionary.TryGetValue(binder.Name, out result);
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        if (!dictionary.ContainsKey(binder.Name))
            return false;
        dictionary[binder.Name] = value;
        return true;
    }
}

然后你的对象就有你想要的属性了。

dynamic o = new MyExpando();
Console.WriteLine("Id :  " + o.Id + ", Title : " + o.Title + ", Description : " + o.Description);

当然，缺点是在编译时没有类型检查，也没有在编译时检查成员是否存在。

Answer 5

现在，每月至少有一次有人询问如何在运行时创建匿名类型...这是回复：

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;

/// <summary>
/// The code generated should be nearly equal to the one generated by
/// csc 12.0.31101.0 when compiling with /optimize+ /debug-. The main
/// difference is in the GetHashCode() (the base init_hash used is 
/// compiler-dependant) and in the maxstack of the generated methods.
/// Note that Roslyn (at least the one present at 
/// tryroslyn.azurewebsites.net) generates different code for anonymous
/// types.
/// </summary>
public static class AnonymousType
{
    private static readonly ConcurrentDictionary<string, Type> GeneratedTypes = new ConcurrentDictionary<string, Type>();

    private static readonly AssemblyBuilder AssemblyBuilder;
    private static readonly ModuleBuilder ModuleBuilder;
    private static readonly string FileName;

    // Some objects we cache
    private static readonly CustomAttributeBuilder CompilerGeneratedAttributeBuilder = new CustomAttributeBuilder(typeof(CompilerGeneratedAttribute).GetConstructor(Type.EmptyTypes), new object[0]);
    private static readonly CustomAttributeBuilder DebuggerBrowsableAttributeBuilder = new CustomAttributeBuilder(typeof(DebuggerBrowsableAttribute).GetConstructor(new[] { typeof(DebuggerBrowsableState) }), new object[] { DebuggerBrowsableState.Never });
    private static readonly CustomAttributeBuilder DebuggerHiddenAttributeBuilder = new CustomAttributeBuilder(typeof(DebuggerHiddenAttribute).GetConstructor(Type.EmptyTypes), new object[0]);

    private static readonly ConstructorInfo ObjectCtor = typeof(object).GetConstructor(Type.EmptyTypes);
    private static readonly MethodInfo ObjectToString = typeof(object).GetMethod("ToString", BindingFlags.Instance | BindingFlags.Public, null, Type.EmptyTypes, null);

    private static readonly ConstructorInfo StringBuilderCtor = typeof(StringBuilder).GetConstructor(Type.EmptyTypes);
    private static readonly MethodInfo StringBuilderAppendString = typeof(StringBuilder).GetMethod("Append", BindingFlags.Instance | BindingFlags.Public, null, new[] { typeof(string) }, null);
    private static readonly MethodInfo StringBuilderAppendObject = typeof(StringBuilder).GetMethod("Append", BindingFlags.Instance | BindingFlags.Public, null, new[] { typeof(object) }, null);

    private static readonly Type EqualityComparer = typeof(EqualityComparer<>);
    private static readonly Type EqualityComparerGenericArgument = EqualityComparer.GetGenericArguments()[0];
    private static readonly MethodInfo EqualityComparerDefault = EqualityComparer.GetMethod("get_Default", BindingFlags.Static | BindingFlags.Public, null, Type.EmptyTypes, null);
    private static readonly MethodInfo EqualityComparerEquals = EqualityComparer.GetMethod("Equals", BindingFlags.Instance | BindingFlags.Public, null, new[] { EqualityComparerGenericArgument, EqualityComparerGenericArgument }, null);
    private static readonly MethodInfo EqualityComparerGetHashCode = EqualityComparer.GetMethod("GetHashCode", BindingFlags.Instance | BindingFlags.Public, null, new[] { EqualityComparerGenericArgument }, null);

    private static int Index = -1;

    static AnonymousType()
    {
        var assemblyName = new AssemblyName("AnonymousTypes");

        FileName = assemblyName.Name + ".dll";

        AssemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndSave);
        ModuleBuilder = AssemblyBuilder.DefineDynamicModule("AnonymousTypes", FileName);
    }

    public static void Dump()
    {
        AssemblyBuilder.Save(FileName);
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="types"></param>
    /// <param name="names"></param>
    /// <returns></returns>
    public static Type CreateType(Type[] types, string[] names)
    {
        if (types == null)
        {
            throw new ArgumentNullException("types");
        }

        if (names == null)
        {
            throw new ArgumentNullException("names");
        }

        if (types.Length != names.Length)
        {
            throw new ArgumentException("names");
        }

        // Anonymous classes are generics based. The generic classes
        // are distinguished by number of parameters and name of 
        // parameters. The specific types of the parameters are the 
        // generic arguments. We recreate this by creating a fullName
        // composed of all the property names, separated by a "|"
        string fullName = string.Join("|", names.Select(x => Escape(x)));

        Type type;

        if (!GeneratedTypes.TryGetValue(fullName, out type))
        {
            // We create only a single class at a time, through this lock
            // Note that this is a variant of the double-checked locking.
            // It is safe because we are using a thread safe class.
            lock (GeneratedTypes)
            {
                if (!GeneratedTypes.TryGetValue(fullName, out type))
                {
                    int index = Interlocked.Increment(ref Index);

                    string name = names.Length != 0 ? string.Format("<>f__AnonymousType{0}`{1}", index, names.Length) : string.Format("<>f__AnonymousType{0}", index);
                    TypeBuilder tb = ModuleBuilder.DefineType(name, TypeAttributes.AnsiClass | TypeAttributes.Class | TypeAttributes.AutoLayout | TypeAttributes.NotPublic | TypeAttributes.Sealed | TypeAttributes.BeforeFieldInit);
                    tb.SetCustomAttribute(CompilerGeneratedAttributeBuilder);

                    GenericTypeParameterBuilder[] generics = null;

                    if (names.Length != 0)
                    {
                        string[] genericNames = Array.ConvertAll(names, x => string.Format("<{0}>j__TPar", x));
                        generics = tb.DefineGenericParameters(genericNames);
                    }
                    else
                    {
                        generics = new GenericTypeParameterBuilder[0];
                    }

                    // .ctor
                    ConstructorBuilder constructor = tb.DefineConstructor(MethodAttributes.Public | MethodAttributes.HideBySig, CallingConventions.HasThis, generics);
                    constructor.SetCustomAttribute(DebuggerHiddenAttributeBuilder);
                    ILGenerator ilgeneratorConstructor = constructor.GetILGenerator();
                    ilgeneratorConstructor.Emit(OpCodes.Ldarg_0);
                    ilgeneratorConstructor.Emit(OpCodes.Call, ObjectCtor);

                    var fields = new FieldBuilder[names.Length];

                    // There are two for cycles because we want to have
                    // all the getter methods before all the other 
                    // methods
                    for (int i = 0; i < names.Length; i++)
                    {
                        // field
                        fields[i] = tb.DefineField(string.Format("<{0}>i__Field", names[i]), generics[i], FieldAttributes.Private | FieldAttributes.InitOnly);
                        fields[i].SetCustomAttribute(DebuggerBrowsableAttributeBuilder);

                        // .ctor
                        constructor.DefineParameter(i + 1, ParameterAttributes.None, names[i]);
                        ilgeneratorConstructor.Emit(OpCodes.Ldarg_0);

                        if (i == 0)
                        {
                            ilgeneratorConstructor.Emit(OpCodes.Ldarg_1);
                        }
                        else if (i == 1)
                        {
                            ilgeneratorConstructor.Emit(OpCodes.Ldarg_2);
                        }
                        else if (i == 2)
                        {
                            ilgeneratorConstructor.Emit(OpCodes.Ldarg_3);
                        }
                        else if (i < 255)
                        {
                            ilgeneratorConstructor.Emit(OpCodes.Ldarg_S, (byte)(i + 1));
                        }
                        else
                        {
                            // Ldarg uses a ushort, but the Emit only
                            // accepts short, so we use a unchecked(...),
                            // cast to short and let the CLR interpret it
                            // as ushort
                            ilgeneratorConstructor.Emit(OpCodes.Ldarg, unchecked((short)(i + 1)));
                        }

                        ilgeneratorConstructor.Emit(OpCodes.Stfld, fields[i]);

                        // getter
                        MethodBuilder getter = tb.DefineMethod(string.Format("get_{0}", names[i]), MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.SpecialName, CallingConventions.HasThis, generics[i], Type.EmptyTypes);
                        ILGenerator ilgeneratorGetter = getter.GetILGenerator();
                        ilgeneratorGetter.Emit(OpCodes.Ldarg_0);
                        ilgeneratorGetter.Emit(OpCodes.Ldfld, fields[i]);
                        ilgeneratorGetter.Emit(OpCodes.Ret);

                        PropertyBuilder property = tb.DefineProperty(names[i], PropertyAttributes.None, CallingConventions.HasThis, generics[i], Type.EmptyTypes);
                        property.SetGetMethod(getter);
                    }

                    // ToString()
                    MethodBuilder toString = tb.DefineMethod("ToString", MethodAttributes.Public | MethodAttributes.Virtual | MethodAttributes.HideBySig, CallingConventions.HasThis, typeof(string), Type.EmptyTypes);
                    toString.SetCustomAttribute(DebuggerHiddenAttributeBuilder);
                    ILGenerator ilgeneratorToString = toString.GetILGenerator();

                    ilgeneratorToString.DeclareLocal(typeof(StringBuilder));

                    ilgeneratorToString.Emit(OpCodes.Newobj, StringBuilderCtor);
                    ilgeneratorToString.Emit(OpCodes.Stloc_0);

                    // Equals
                    MethodBuilder equals = tb.DefineMethod("Equals", MethodAttributes.Public | MethodAttributes.Virtual | MethodAttributes.HideBySig, CallingConventions.HasThis, typeof(bool), new[] { typeof(object) });
                    equals.SetCustomAttribute(DebuggerHiddenAttributeBuilder);
                    equals.DefineParameter(1, ParameterAttributes.None, "value");
                    ILGenerator ilgeneratorEquals = equals.GetILGenerator();
                    ilgeneratorEquals.DeclareLocal(tb);

                    ilgeneratorEquals.Emit(OpCodes.Ldarg_1);
                    ilgeneratorEquals.Emit(OpCodes.Isinst, tb);
                    ilgeneratorEquals.Emit(OpCodes.Stloc_0);
                    ilgeneratorEquals.Emit(OpCodes.Ldloc_0);

                    Label equalsLabel = ilgeneratorEquals.DefineLabel();

                    // GetHashCode()
                    MethodBuilder getHashCode = tb.DefineMethod("GetHashCode", MethodAttributes.Public | MethodAttributes.Virtual | MethodAttributes.HideBySig, CallingConventions.HasThis, typeof(int), Type.EmptyTypes);
                    getHashCode.SetCustomAttribute(DebuggerHiddenAttributeBuilder);
                    ILGenerator ilgeneratorGetHashCode = getHashCode.GetILGenerator();
                    ilgeneratorGetHashCode.DeclareLocal(typeof(int));

                    if (names.Length == 0)
                    {
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldc_I4_0);
                    }
                    else
                    {
                        // As done by Roslyn
                        // Note that initHash can vary, because
                        // string.GetHashCode() isn't "stable" for 
                        // different compilation of the code
                        int initHash = 0;

                        for (int i = 0; i < names.Length; i++)
                        {
                            initHash = unchecked(initHash * (-1521134295) + fields[i].Name.GetHashCode());
                        }

                        // Note that the CSC seems to generate a 
                        // different seed for every anonymous class
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldc_I4, initHash);
                    }

                    for (int i = 0; i < names.Length; i++)
                    {
                        // Equals()
                        Type equalityComparerT = EqualityComparer.MakeGenericType(generics[i]);
                        MethodInfo equalityComparerTDefault = TypeBuilder.GetMethod(equalityComparerT, EqualityComparerDefault);
                        MethodInfo equalityComparerTEquals = TypeBuilder.GetMethod(equalityComparerT, EqualityComparerEquals);

                        ilgeneratorEquals.Emit(OpCodes.Brfalse_S, equalsLabel);
                        ilgeneratorEquals.Emit(OpCodes.Call, equalityComparerTDefault);
                        ilgeneratorEquals.Emit(OpCodes.Ldarg_0);
                        ilgeneratorEquals.Emit(OpCodes.Ldfld, fields[i]);
                        ilgeneratorEquals.Emit(OpCodes.Ldloc_0);
                        ilgeneratorEquals.Emit(OpCodes.Ldfld, fields[i]);
                        ilgeneratorEquals.Emit(OpCodes.Callvirt, equalityComparerTEquals);

                        // GetHashCode();
                        MethodInfo EqualityComparerTGetHashCode = TypeBuilder.GetMethod(equalityComparerT, EqualityComparerGetHashCode);

                        ilgeneratorGetHashCode.Emit(OpCodes.Stloc_0);
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldc_I4, -1521134295);
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldloc_0);
                        ilgeneratorGetHashCode.Emit(OpCodes.Mul);
                        ilgeneratorGetHashCode.Emit(OpCodes.Call, equalityComparerTDefault);
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldarg_0);
                        ilgeneratorGetHashCode.Emit(OpCodes.Ldfld, fields[i]);
                        ilgeneratorGetHashCode.Emit(OpCodes.Callvirt, EqualityComparerTGetHashCode);
                        ilgeneratorGetHashCode.Emit(OpCodes.Add);

                        // ToString()
                        ilgeneratorToString.Emit(OpCodes.Ldloc_0);
                        ilgeneratorToString.Emit(OpCodes.Ldstr, i == 0 ? string.Format("{{ {0} = ", names[i]) : string.Format(", {0} = ", names[i]));
                        ilgeneratorToString.Emit(OpCodes.Callvirt, StringBuilderAppendString);
                        ilgeneratorToString.Emit(OpCodes.Pop);
                        ilgeneratorToString.Emit(OpCodes.Ldloc_0);
                        ilgeneratorToString.Emit(OpCodes.Ldarg_0);
                        ilgeneratorToString.Emit(OpCodes.Ldfld, fields[i]);
                        ilgeneratorToString.Emit(OpCodes.Box, generics[i]);
                        ilgeneratorToString.Emit(OpCodes.Callvirt, StringBuilderAppendObject);
                        ilgeneratorToString.Emit(OpCodes.Pop);
                    }

                    // .ctor
                    ilgeneratorConstructor.Emit(OpCodes.Ret);

                    // Equals()
                    if (names.Length == 0)
                    {
                        ilgeneratorEquals.Emit(OpCodes.Ldnull);
                        ilgeneratorEquals.Emit(OpCodes.Ceq);
                        ilgeneratorEquals.Emit(OpCodes.Ldc_I4_0);
                        ilgeneratorEquals.Emit(OpCodes.Ceq);
                    }
                    else
                    {
                        ilgeneratorEquals.Emit(OpCodes.Ret);
                        ilgeneratorEquals.MarkLabel(equalsLabel);
                        ilgeneratorEquals.Emit(OpCodes.Ldc_I4_0);
                    }

                    ilgeneratorEquals.Emit(OpCodes.Ret);

                    // GetHashCode()
                    ilgeneratorGetHashCode.Emit(OpCodes.Stloc_0);
                    ilgeneratorGetHashCode.Emit(OpCodes.Ldloc_0);
                    ilgeneratorGetHashCode.Emit(OpCodes.Ret);

                    // ToString()
                    ilgeneratorToString.Emit(OpCodes.Ldloc_0);
                    ilgeneratorToString.Emit(OpCodes.Ldstr, names.Length == 0 ? "{ }" : " }");
                    ilgeneratorToString.Emit(OpCodes.Callvirt, StringBuilderAppendString);
                    ilgeneratorToString.Emit(OpCodes.Pop);
                    ilgeneratorToString.Emit(OpCodes.Ldloc_0);
                    ilgeneratorToString.Emit(OpCodes.Callvirt, ObjectToString);
                    ilgeneratorToString.Emit(OpCodes.Ret);

                    type = tb.CreateType();

                    type = GeneratedTypes.GetOrAdd(fullName, type);
                }
            }
        }

        if (types.Length != 0)
        {
            type = type.MakeGenericType(types);
        }

        return type;
    }

    private static string Escape(string str)
    {
        // We escape the \ with \\, so that we can safely escape the
        // "|" (that we use as a separator) with "\|"
        str = str.Replace(@"\", @"\\");
        str = str.Replace(@"|", @"\|");
        return str;
    }
}

这个又大又胖的代码块将在运行时使用Reflection.Emit 生成一些具有任意命名属性的类（您甚至可以使用C# 中非法的字符）。这些类将遵循 C# 编译器 12.0.31101.0 生成的匿名类的命名约定。即使在 IL 级别，它们也应该几乎相等。所有各种Equals()、GetHashCode() 和ToString() 都是由C# 编译器12.0.31101.0 实现的，所有字段都具有相同的名称，插入了CompilerGeneratedAttribute（这在道德上是错误的，我知道：- ） ） 等等。所以这些类生成了walk like an anonymous duck 并且像一只匿名鸭子一样嘎嘎......它们实际上是匿名鸭子:-)（请注意，罗斯林鸭子属于不同的亚种......它们的羽毛有点不同......一只匿名鸭子鉴赏家可以轻松区分这两个亚种:-)）

现在，如果您想问cui prodest? 生成的类只能通过反射使用，因此很难使用，但是它们有一个特定的用例，即 Marc Gravell 个性化：. NET 框架，大量使用反射来呈现对象（例如所有各种数据网格）。这些部分与dynamic 对象不兼容，并且通常不支持object[]。解决方案通常是将数据封装在 DataTable... 中，或者您可以使用它:-)

在您的具体情况下，您可以使用此方法：

public static object FromDictToAnonymousObj<TValue>(IDictionary<string, TValue> dict)
{
    var types = new Type[dict.Count];

    for (int i = 0; i < types.Length; i++)
    {
        types[i] = typeof(TValue);
    }

    // dictionaries don't have an order, so we force an order based
    // on the Key
    var ordered = dict.OrderBy(x => x.Key).ToArray();

    string[] names = Array.ConvertAll(ordered, x => x.Key);

    Type type = AnonymousType.CreateType(types, names);

    object[] values = Array.ConvertAll(ordered, x => (object)x.Value);

    object obj = type.GetConstructor(types).Invoke(values);

    return obj;
}

像这样：

var dict = new Dictionary<string, string>
{
    {"Id", "1"},
    {"Title", "My title"},
    {"Description", "Blah blah blah"},
};

object obj1 = FromDictToAnonymousObj(dict);

获取你的对象。