Customized method to convert Json string to C# object-C#.Net Tutorial-php.cn

Customized method to convert Json string to C# object

高洛峰

Release： 2017-01-18 09:56:22

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Atrribute is used here to convert Json strings into C# objects. Due to functional limitations, this version is only for Json strings, such as "response":"Hello","id":21231513,"result":100,"msg":"OK."; rather than Json arrays. The Atrribute here acts on the attribute. Like the Atrribute in NHibernate, it uses reflection at runtime to obtain which key in the Json string this attribute corresponds to.

namespace JsonMapper
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
    public class JsonFieldAttribute : Attribute
    {
        private string _Name = string.Empty;
        public string Name
        {
            get { return _Name; }
            set { _Name = value; }
        }
    }
}

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The next step is the conversion tool The core code mainly decomposes and analyzes the key and value in the Json string, and obtains and assigns each corresponding attribute in the object through reflection.

namespace JsonMapper
{
    public class JsonToInstance
    {
        public T ToInstance<T>(string json) where T : new()
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            string[] fields = json.Split(&#39;,&#39;);
            for (int i = 0; i < fields.Length; i++ )
            {
                string[] keyvalue = fields[i].Split(&#39;:&#39;);
                dic.Add(Filter(keyvalue[0]), Filter(keyvalue[1]));
            }
            PropertyInfo[] properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
            T entity = new T();
            foreach (PropertyInfo property in properties)
            {
                object[] propertyAttrs = property.GetCustomAttributes(false);
                for (int i = 0; i < propertyAttrs.Length; i++) 
                {
                    object propertyAttr = propertyAttrs[i];
                    if (propertyAttr is JsonFieldAttribute)
                    {
                        JsonFieldAttribute jsonFieldAttribute = propertyAttr as JsonFieldAttribute;
                        foreach (KeyValuePair<string ,string> item in dic)
                        {
                            if (item.Key == jsonFieldAttribute.Name)
                            {
                                Type t = property.PropertyType;
                                property.SetValue(entity, ToType(t, item.Value), null);
                                break;
                            }
                        }
                    }
                }
            }
            return entity;
        }
        private string Filter(string str)
        {
            if (!(str.StartsWith("\"") && str.EndsWith("\"")))
            {
                return str;
            }
            else 
            {
                return str.Substring(1, str.Length - 2);
            }
        }
        public object ToType(Type type, string value)
        {
            if (type == typeof(string))
            {
                return value;
            }
            MethodInfo parseMethod = null;
            foreach (MethodInfo mi in type.GetMethods(BindingFlags.Static 
                | BindingFlags.Public))
            {
                if (mi.Name == "Parse" && mi.GetParameters().Length == 1)
                {
                    parseMethod = mi;
                    break;
                }
            }
            if (parseMethod == null)
            {
                throw new ArgumentException(string.Format(
                    "Type: {0} has not Parse static method!", type));
            }
            return parseMethod.Invoke(null, new object[] { value });
        }
    }
}

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Finally this is the code for testing

public class Message
    {
        //{ "result": 100, "response": "Who are you?!", "id": 13185569, "msg": "OK." }
        [JsonField(Name = "result")]
        public int Result { get; set; }
        [JsonField(Name = "response")]
        public string Response { get; set; }
        [JsonField(Name = "id")]
        public int Id { get; set; }
        [JsonField(Name = "msg")]
        public string Msg { get; set; }
    }

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class Program
    {
        static void Main(string[] args)
        {
            JsonToInstance util = new JsonToInstance();
            string json = "\"response\":\"我是阿猫酱的小黄鸡\",\"id\":21231513,\"result\":100,\"msg\":\"OK.\"";
            Message m = util.ToInstance<Message>(json);
        }
    }

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