在ASP.NET 5 DNX Core Azure Tables中使用自定義屬性類型

Question

Azure表存儲does not support許多屬性類型（列表<>，TimeSpan等）。

有像Lucifure Stash和Lokad.Cloud這樣的解決方案，但它們不針對DNX Core 5.0進行編譯。

有沒有辦法在使用DNX Core的Azure Tables中添加對自定義屬性類型的支持？

Answer 1

一個解決方案是使用反射遍歷實體的所有「自定義」屬性，並將它們序列化爲JSON字符串。

我們可以覆蓋TableEntity的ReadEntity和WriteEntity方法來勾去/系列化：

using System; 
using System.Linq; 
using System.Reflection; 
using System.Collections.Generic; 
using Microsoft.WindowsAzure.Storage; 
using Microsoft.WindowsAzure.Storage.Table; 
using Newtonsoft.Json; 
using Newtonsoft.Json.Linq; 

public abstract class CustomEntity : TableEntity 
{ 
    public override IDictionary<string, EntityProperty> WriteEntity (OperationContext operationContext) 
    { 
     var properties = base.WriteEntity(operationContext); 

     // Iterating through the properties of the entity 
     foreach (var property in GetType().GetProperties().Where(property => 
       // Excluding props explicitly marked to ignore serialization 
       !property.GetCustomAttributes<IgnorePropertyAttribute>(true).Any() && 
       // Excluding already serialized props 
       !properties.ContainsKey(property.Name) && 
       // Excluding internal TableEntity props 
       typeof(TableEntity).GetProperties().All(p => p.Name != property.Name))) 
     { 
      var value = property.GetValue(this); 
      if (value != null) 
       // Serializing property to JSON 
       properties.Add(property.Name, new EntityProperty(JsonConvert.SerializeObject(value))); 
     } 

     return properties; 
    } 

    public override void ReadEntity (IDictionary<string, EntityProperty> properties, OperationContext operationContext) 
    { 
     base.ReadEntity(properties, operationContext); 

     // Iterating through the properties of the entity 
     foreach (var property in GetType().GetProperties().Where(property => 
       // Excluding props explicitly marked to ignore serialization 
       !property.GetCustomAttributes<IgnorePropertyAttribute>(true).Any() && 
       // Excluding props which were not originally serialized 
       properties.ContainsKey(property.Name) && 
       // Excluding props with target type of string (they are natively supported) 
       property.PropertyType != typeof(string) && 
       // Excluding non-string table fields (this will filter-out 
       // all the remaining natively supported props like byte, DateTime, etc) 
       properties[property.Name].PropertyType == EdmType.String)) 
     { 
      // Checking if property contains a valid JSON 
      var jToken = TryParseJson(properties[property.Name].StringValue); 
      if (jToken != null) 
      { 
       // Constructing method for deserialization 
       var toObjectMethod = jToken.GetType().GetMethod("ToObject", new[] { typeof(Type) }); 
       // Invoking the method with the target property type; eg, jToken.ToObject(CustomType) 
       var value = toObjectMethod.Invoke(jToken, new object[] { property.PropertyType }); 

       property.SetValue(this, value); 
      } 
     } 
    } 

    private static JToken TryParseJson (string s) 
    { 
     try { return JToken.Parse(s); } 
     catch (JsonReaderException) { return null; } 
    } 
} 

現在，如果我們從CustomEntity類繼承我們的表實體，我們可以自由的使用性能與支持的任何類型由Json.NET提供。