Configuration binding of type Dictionary<string, object> fails if value is List

[ti82]

Using this POCO settings class:

public class RuntimeSettings
{
    public string Type { get; set; }
    public Dictionary<string, object> Parameters { get; set; }
}

Using object as the value type lets this be more generic and support strings, ints, bools, etc.

And a settings JSON file like this:

{
  "Type": "MyRuntimeType",
  "Parameters": {
    "param1": true,
    "param2": [ "Hello", "World" ]
  }
}

I get a ArgumentNullException when binding the configuration like this.

[ti82]

Here is the call stack just below my code:

Unhandled Exception: System.ArgumentNullException: Value cannot be null.
Parameter name: type
at System.Reflection.IntrospectionExtensions.GetTypeInfo(Type type)
at Microsoft.Extensions.Configuration.ConfigurationBinder.GetAllProperties(TypeInfo type)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar(IConfiguration configuration, Object instance)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindDictionary(Object dictionary, Type dictionaryType, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindProperty(PropertyInfo property, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar(IConfiguration configuration, Object instance)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindProperty(PropertyInfo property, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar(IConfiguration configuration, Object instance)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config)
at Microsoft.Extensions.Configuration.ConfigurationBinder.Bind(IConfiguration configuration, Object instance)
at Microsoft.Extensions.Options.OptionsFactory1.Create(String name) at System.Lazy1.ViaFactory(LazyThreadSafetyMode mode)
at System.Lazy1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor) at System.Lazy1.CreateValue()

[dnasir]

I'm experiencing this with nested dictionaries as well.

[davidfowl]

The configuration system doesn't have any types (well it has strings and IConfigurationSections) and relies on the target type in order to do the appropriate conversion. The only reasonable thing to bind here would be an IConfigurationSection since the target type is object.

In the above example, param1 is typed as string because it has no inherent type.

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