Looping through JSON array and adding items to list C#

Question

Sorry for basic question, I'm beginner and tried to find my problem, but wasn't able to

string json = "{\"EmailList\":[{\"name\":\"John Bravo\",\"email\":\"[email protected]\"},{\"name\":\"Daniel Alutcher\",\"email\":\"[email protected]\"},{\"name\":\"James Rodriguez\",\"email\":\"[email protected]\"}]}";

JObject rss = JObject.Parse(json);

var data = JsonConvert.DeserializeObject<dynamic>(json);

dynamic emails = data.EmailList;

List<string> emailList = new List<string>();

foreach (dynamic item in emails)
{
    int x = 0;
    if (item.email != null)
    {
        Console.WriteLine(item.email);
        //emailList.Add(item.email); // throws exception System.Collections.Generic.List<string>.Add(string)' has some invalid arguments' 
    }
}

So I'm looping trough this JSON and I'm able to get in console each email, but when I'm trying to add it to a list, it's throwing exception error

@Leron_says_get_back_Monica While that will get rid of the exception, the list will be full of nulls, since the dynamic objects aren't strings as such. — Lasse V. Karlsen
– Lasse V. Karlsen, Commented Oct 22, 2020 at 14:06
You can simplify this whole question down to this code: dynamic test = new JValue("Test"); new List<string>().Add(test);, and I wonder why that fails, since string s = test; works just fine. — Lasse V. Karlsen
– Lasse V. Karlsen, Commented Oct 22, 2020 at 14:08

Drag and Drop · Accepted Answer · 2020-10-22 15:03:31Z

1

As you commented "IS there any way to avoid "dynamic" in this code?".

Well there is and it's pretty simple, It's a simple copy past!
In Visual Studio using the special past in top bar menu (image).
Or in an online tool like app.quicktype.io or json2csharp.com.

using  Newtonsoft.Json;

public partial class JsonData //Give it a better name
{
       [JsonProperty("EmailList")] public List<EmailInformation> EmailList { get; set; }
}

public partial class EmailInformation
{
       [JsonProperty("name")]  public string Name { get; set; } 
       [JsonProperty("email")] public string Email { get; set; }
}

And the usage is pretty straightforward too, and you already have most of it in your code:

var data = JsonConvert.DeserializeObject<JsonData>(json);

foreach(var mailInfo  in data.EmailList){
       Console.WriteLine($"{mailInfo.Name} <{mailInfo.Email}>;");
}

//here a list of string 
var emails = data.EmailList.Select(x=> x.Email).ToList();

edited Oct 22, 2020 at 15:03

answered Oct 22, 2020 at 14:58

Drag and Drop

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3 Comments

onlyo Over a year ago

Thank you! This is exactly what I needed :)

onlyo Over a year ago

and what if this JSON would be in Appsettings as a part of whole appsettings json? How would be it possible to import it to Program.cs ?

Drag and Drop Over a year ago

@onlyo, you are on Core? How to read AppSettings values from a .json file. Then The documentation will be the thing to check learn.microsoft.com/en-us/aspnet/core/fundamentals/…. Hierachical and Bind an array will be a must read.

Mihir Dave · Accepted Answer · 2020-10-22 13:56:24Z

0

You're Trying to add dynamic in List<string> instead you should do

emailList.Add(item.email.ToString());

Code:

string json =
"{\"EmailList\":[{\"name\":\"John Bravo\",\"email\":\"[email protected]\"},{\"name\":\"Daniel Alutcher\",\"email\":\"[email protected]\"},{\"name\":\"James Rodriguez\",\"email\":\"[email protected]\"}]}";


JObject rss = JObject.Parse(json);

var data = JsonConvert.DeserializeObject<dynamic>(json);

dynamic emails = data.EmailList;

List<string> emailList = new List<string>();

foreach (dynamic item in emails)
{
    int x = 0;
    if (item.email != null)
    {
        Console.WriteLine(item.email);
        emailList.Add(item.email.ToString()); // Change here 
   }
}

answered Oct 22, 2020 at 13:56

Mihir Dave

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11 Comments

Lasse V. Karlsen Over a year ago

I am wondering why .Add((string)item.email) works just fine, but .Add(item.email) doesn't.

Mihir Dave Over a year ago

@LasseV.Karlsen IMO item.email in the current state has type dynamic which is not string what Add requires. so we explicitly need to cast that.

Lasse V. Karlsen Over a year ago

Adding dynamic to a List<string> should really work just fine, assuming the value in the dynamic is coercible to a string. For instance, you can do this, and it works: string s = item.email; The underlying object is of type JValue, but again, it works when assigning directly to a string variable, so I wonder why it doesn't allow this when calling a method that only accepts a string parameter.

Lasse V. Karlsen Over a year ago

I asked a new question instead - stackoverflow.com/questions/64484213/…

Mihir Dave Over a year ago

@LasseV.Karlsen I didn't see your edited comment about JValue, now I'm as much curious as you're, following your asked question. thanks for asking this.

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