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?

Answer 1

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"
  }