System.InvalidOperationException if configuration has dictionary with colon in key.

[Andrey Kudashkin]

Hi.
I got a error when I tried to read an object from the configuration that was loaded from the json file.
I wrote simple config file:

testdata.json:

{
  "Urls": {
    "https://site.com": "here are description for site.com",
    "https://example.com": "here are description for example.com"
  } 
}

And I wrote simple program for read that config file:
Program.cs

class Program
    {
        static void Main(string[] args)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("testdata.json", true, true);
            
            var config = builder.Build();
            var initialData = config.Get<TestData>();

            foreach (var urlData in initialData.Urls)
            {
                Console.WriteLine($"{urlData.Key} - {urlData.Value}");
            }
        }
    }

    public class TestData
    {
        public Dictionary<string, string> Urls { get; set; } 
    }

During the call to config.Get (), I get an error System.InvalidOperationException: 'Cannot create instance of type 'System.String' because it is missing a public parameterless constructor.'
It happens in https://github.com/aspnet/Configuration/blob/rel/2.0.0/src/Microsoft.Extensions.Configuration.Binder/ConfigurationBinder.cs#L366
because keys of my configuration's dictionary contains colon.

ConfigurationPath has propery KeyDelimiter = ":", ConfigurationBinder uses it to separate individual keys in a path and because of this, the ConfigurationBinder.BindDictionary method tries to create an instance of the string instead of the KeyValuePair instance.

My main question.

Is this behavior as designed and I can not use colons in the dictionary keys?
Or it is a bug and I can try to fix this bug in ConfigurationBinder?

[Arthur Vickers]

@neyromant Colons are reserved for special meaning in the keys, so they shouldn't be used as part of normal key values.