How to get attribute in C# object like javascript?

Question

There is a function I want to implement in C#:

public string getName(object ob)
{
    // TODO: if object has "Name" attribute, return "Name".Value, else return null;
}

When I invoke this function,

string result1 = getName(new {Name = "jack", Age = 12})     // result1 = "jack"
string result2 = getName(new {Age = 12})      // result2 = null

I know it's easy to implement in JavaScript or other dynamic languages... I am curious about if it can implement in C#?

What is the expected result for getName(new {Name = new MyCustomObject()})? — grek40
– grek40, Commented Jun 22, 2018 at 6:02
@grek40 I didn't consider it... But the answer is enough for me now. I just want to know if can implement it... — pwxcoo
– pwxcoo, Commented Jun 22, 2018 at 6:09

Rumpelstinsk · Accepted Answer · 2018-06-22 05:58:36Z

5

Yes, you can. Take a look to Reflection

public string getName(object ob)
{
    var type = ob.GetType();
    if (type.GetProperty("Name") == null) return null;
    else return type.GetProperty("Name").GetValue(ob, null);
}

answered Jun 22, 2018 at 5:58

Rumpelstinsk

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Comments

SᴇM · Accepted Answer · 2018-06-22 06:10:26Z

2

There is several ways to achieve that. For example by using reflection. It will take one line code:

public static string GetName(object ob) =>
    ob.GetType().GetProperty("Name")?.GetValue(ob)?.ToString();

Or below c#6 way:

public static string GetName(object ob)
{
    return ob.GetType().GetProperty("Name")?.GetValue(ob)?.ToString();
}

You can even serialize your object to JSON or XML, then try to get your value from that:

public static string GetName(object obj)
{
    string json = JsonConvert.SerializeObject(obj);
    string result = JsonConvert.DeserializeAnonymousType(json, new { Name = "" })?.Name;
    return result;
}

edited Jun 22, 2018 at 6:10

answered Jun 22, 2018 at 6:04

SᴇM

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Comments

AD8 · Accepted Answer · 2018-06-22 06:08:02Z

1

UPDATE: While this may work for your needs, it is probably not the best solution as pointed out by Grek40, and Damien_The_Unbeliever in comments below due to several limitations. Not completely deleting the answer as it may give you some information about the alternative despite of its limitations.

Original Answer:

Try this.. Rextester can be found -- http://rextester.com/DQOBW76322

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {

            string result1 = getName(new {Name = "jack", Age = 12});    // result1 = "jack"
            string result2 = getName(new {Age = 12});

            Console.WriteLine(result1);
            Console.WriteLine(result2);
        }

        public static string getName(object obj)
        {
            var testData = obj.GetType().GetProperties().ToDictionary(p => p.Name, p => p.GetValue(obj).ToString());

            if(testData.Any(d => d.Key == "Name")){
                return testData["Name"];
            }

            return null;
        }
    }
}

edited Jun 22, 2018 at 6:08

answered Jun 22, 2018 at 5:58

AD8

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4 Comments

grek40 Over a year ago

Isn't it a bit of overkill to first invoke all property getters before deciding which to use?

AD8 Over a year ago

@grek40, just realized it. Could potentially be made much simpler (or efficient rather, will update the answer soon.)

Damien_The_Unbeliever Over a year ago

And it'll throw if the class has any set-only properties (which, yes, I know, are evil, but can exist)

AD8 Over a year ago

@Damien_The_Unbeliever Didn't think of that either, just updated the answer about this limitation. Thanks for pointing this out.

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