序列化MongoDb上的get-only属性

Question

使用C＃6，我可以写：

public class Person
{
    public Guid Id { get; }
    public string Name { get; }
    public Person(Guid id, string name)
    {
        Id = id;
        Name = name;
    }
}

不幸的是，像MongoDb驱动程序没有正确序列化这样的类，属性没有被序列化。

MongoDb仅使用getter和setter通过默认属性进行序列化。我知道你可以手动更改类映射并告诉序列化器到include get-only properties但我正在寻找一种通用的方法来避免自定义每个映射。

我想创建一个类似于ReadWriteMemberFinderConvention但没有CanWrite检查的自定义约定。

还有其他解决方案吗？构造函数会自动调用，还是需要其他一些自定义？

Answer 1

我试图通过创建一个约定来解决这个问题，该约定映射了与构造函数匹配的所有只读属性以及匹配的构造函数。

假设你有一个不可变的类，如：

public class Person
{
    public string FirstName { get; }
    public string LastName { get; }
    public string FullName => FirstName + LastName;
    public ImmutablePocoSample(string lastName)
    {
        LastName = lastName;
    }

    public ImmutablePocoSample(string firstName, string lastName)
    {
        FirstName = firstName;
        LastName = lastName;
    }
}

这是约定的代码：

using MongoDB.Bson.Serialization;
using MongoDB.Bson.Serialization.Conventions;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

/// <summary>
/// A convention that map all read only properties for which a matching constructor is found.
/// Also matching constructors are mapped.
/// </summary>
public class ImmutablePocoConvention : ConventionBase, IClassMapConvention
{
    private readonly BindingFlags _bindingFlags;

    public ImmutablePocoConvention()
            : this(BindingFlags.Instance | BindingFlags.Public)
    { }

    public ImmutablePocoConvention(BindingFlags bindingFlags)
    {
        _bindingFlags = bindingFlags | BindingFlags.DeclaredOnly;
    }

    public void Apply(BsonClassMap classMap)
    {
        var readOnlyProperties = classMap.ClassType.GetTypeInfo()
            .GetProperties(_bindingFlags)
            .Where(p => IsReadOnlyProperty(classMap, p))
            .ToList();

        foreach (var constructor in classMap.ClassType.GetConstructors())
        {
            // If we found a matching constructor then we map it and all the readonly properties
            var matchProperties = GetMatchingProperties(constructor, readOnlyProperties);
            if (matchProperties.Any())
            {
                // Map constructor
                classMap.MapConstructor(constructor);

                // Map properties
                foreach (var p in matchProperties)
                    classMap.MapMember(p);
            }
        }
    }

    private static List<PropertyInfo> GetMatchingProperties(ConstructorInfo constructor, List<PropertyInfo> properties)
    {
        var matchProperties = new List<PropertyInfo>();

        var ctorParameters = constructor.GetParameters();
        foreach (var ctorParameter in ctorParameters)
        {
            var matchProperty = properties.FirstOrDefault(p => ParameterMatchProperty(ctorParameter, p));
            if (matchProperty == null)
                return new List<PropertyInfo>();

            matchProperties.Add(matchProperty);
        }

        return matchProperties;
    }


    private static bool ParameterMatchProperty(ParameterInfo parameter, PropertyInfo property)
    {
        return string.Equals(property.Name, parameter.Name, System.StringComparison.InvariantCultureIgnoreCase)
               && parameter.ParameterType == property.PropertyType;
    }

    private static bool IsReadOnlyProperty(BsonClassMap classMap, PropertyInfo propertyInfo)
    {
        // we can't read 
        if (!propertyInfo.CanRead)
            return false;

        // we can write (already handled by the default convention...)
        if (propertyInfo.CanWrite)
            return false;

        // skip indexers
        if (propertyInfo.GetIndexParameters().Length != 0)
            return false;

        // skip overridden properties (they are already included by the base class)
        var getMethodInfo = propertyInfo.GetMethod;
        if (getMethodInfo.IsVirtual && getMethodInfo.GetBaseDefinition().DeclaringType != classMap.ClassType)
            return false;

        return true;
    }
}

您可以使用以下方式注册我

ConventionRegistry.Register(
    nameof(ImmutablePocoConvention),
    new ConventionPack { new ImmutablePocoConvention() },
    _ => true);

Answer 2

如果您不希望序列化所有只读属性，则可以添加一个不执行任何操作的公共集（如果适用），只需注意在对类进行反序列化时将重新评估该属性。

public class Person
{
    public string FirstName { get; }
    public string LastName { get; }
    public string FullName
    {
        get
        {
            return FirstName + LastName;
        }
        set
        {
           //this will switch on the serialization
        }
    }
}