Cannot create instance of type 'System.String'

Question

I try to get my section from appsettings.json, and then bind it to the intance of MongoSettings class, but I have an exception which is:

"Cannot create instance of type 'System.String' because it is missing a public parameterless constructor."

It is strange, because I'm using the same method to get jwt settings.

Please take a look:

    var jwtSettings = Configuration.GetSection("jwt").Get<JwtSettings>(); //it works
    var mongoSettings = Configuration.GetSection("mongo").Get<MongoSettings>(); //it doesn't

appsettings.json

  "Jwt": {
    "issuer" : "localhost:5000",
    "expiryMinutes" : 60,
    "key" : "das#@4SD120847@12313"
  },
  "Mongo": {
    "connection:" : "mongodb://localhost:27017",
    "database" : "MemoTime"
  }

MongoSettings:

public class MongoSettings
{
    public string Connection { get; set; }
    public string Database { get; set; }
}

JwtSettings:

public class JwtSettings
{
    public string Key { get; set; }
    public string ValidIssuer { get; set; }
    public int ExpiryMinutes { get; set; }
}

As you can see, both clasess and sections in app settings looks similarly, so why getting settings for mongo does not work?

"issuer" : "localhost:5000", <---> public string ValidIssuer { get; set; } ? — zwcloud
– zwcloud, Commented Dec 12, 2017 at 6:27
Ou...you're right I missed it. But the rest properties are bound properly — bielu000
– bielu000, Commented Dec 12, 2017 at 6:30
Damn, what are the chances, I made the same stupid mistake :') — Andras Toth
– Andras Toth, Commented Dec 11, 2023 at 18:50

Michael Freidgeim · Accepted Answer · 2024-07-21 08:27:43Z

30

You Issue is in Json there is extra colon ":" at the end of key "connection:". That why it is giving error

Valid Json Data.

"Jwt": 
  {
    "issuer": "localhost:5000",
    "expiryMinutes": 60,
    "key": "das#@4SD120847@12313"
  },
  "Mongo": 
  {
    "connection": "mongodb://localhost:27017",
    "database": "MemoTime"
  }

edited Jul 21, 2024 at 8:27

Michael Freidgeim

28.8k17 gold badges164 silver badges181 bronze badges

answered Dec 12, 2017 at 6:51

Saineshwar Bageri - MVP

4,0317 gold badges46 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

bielu000 Over a year ago

You're right. Now it works. How I could missed it...? Thanks :)

zwcloud Over a year ago

What kind of project is this? I tried .NET core console app and added Microsoft.Extensions.Configuration and Microsoft.Extensions.Configuration.Json but error occurs: 'IConfigurationSection' does not contain a definition for 'Get' and no extension method 'Get' accepting a first argument of type 'IConfigurationSection' could be found.

Saineshwar Bageri - MVP Over a year ago

This asp.net core web application

zwcloud Over a year ago

Thanks. I found it to be an ASP.NET MVC project. An empty ASP.NET core web app still can not figure out the Get<T> method. This method is actually declared in Microsoft.Extensions.Configuration.ConfigurationBinder in Microsoft.Extensions.Configuration.Binder.dll.

Saineshwar Bageri - MVP Over a year ago

See Startup class in that project in that you can see ConfigureServices Method where we are going to write code for reading data from appsettings.json file

|

Collectives™ on Stack Overflow

Cannot create instance of type 'System.String'

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related