自定义实现Json字符串向C#对象转变的方法

这里使用atrribute的方式实现了json字符串向c#对象的转变。因为功能局限，此版本只是针对于json字符串,如"response":"hello","id":21231513,"result":100,"msg":"ok."; 而不是json数组。这里的atrribute是作用在属性上，像nhibernate中的atrribute一样，是在运行时通过反射来获取这个属性对应于json字符串中的哪个key.

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; }
        }
    }
}

接下来是这个转换工具中的核心代码，主要是分解并且分析json字符串中key与value, 并且通过反射获得对象中的各个对应属性并且赋值。

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(',');
            for (int i = 0; i < fields.length; i++ )
            {
                string[] keyvalue = fields[i].split(':');
                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 });
        }
    }
}

最后这是用于测试的代码

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; }
    }

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);
        }
    }