> For the complete documentation index, see [llms.txt](https://vostok.gitbook.io/configuration/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vostok.gitbook.io/configuration/binding/classes-and-structs.md).

# Classes and structs

### How it works

The binder starts off by creating an instance of the bound type with default values of public fields and properties (the same way as `Activator.CreateInstance` does) and then recursively binds the value of every field and property to a corresponding subsection of the settings tree. See [binding nodes to models](/configuration/concepts-and-basics/binding-nodes-to-models.md) page for a step-by-step illustration of this process.

Fields and properties don't have to be mutable: readonly fields and properties with private setters (or even without one) are fine.

Following members are **ignored**: indexers, constants, static and non-public fields and properties, computed properties without backing fields.

Nested classes and [collections](/configuration/binding/collections.md) are supported without restrictions.

### Settings tree navigation

When binding a field or property value, the settings tree is [scoped](/configuration/concepts-and-basics/settings-nodes-scoping.md) to the member name. This imposes a requirement to synchronize naming in configuration data provided by [sources](/configuration/concepts-and-basics/configuration-sources.md) and models in the application code. In order to bind a model property named `Timeout` from a section of JSON file, this section must contain a property with the same name (barring case).

```
Model                             JSON data source

class Settings                    {
{
    TimeSpan Timeout { get; } -------> "timeout": "2 seconds",
    
    int Parallelism { get; }  -------> "parallelism": 32
}                                 }
```

[Name aliases](/configuration/advanced-scenarios/use-name-aliases.md) allow to decouple property names from configuration data names.

### Required and optional members

By default all fields and properties are treated as optional: they are just left with default values if no data could be found in the settings tree (default values may come from field and property initializers). It's possible to [make members required](/configuration/basic-scenarios/make-settings-required.md) though. Required members with no data in the settings tree cause the binding process to fail and produce an exception.

### Model requirements

Model classes must either have a parameterless constructor, a constructor with a single parameter, or have an `OmitConstructorsAttribute` (which allows [creating an uninitialized object](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.serialization.formatterservices.getuninitializedobject), therefore, no default parameters are present).

### Binder requirements

Binders are required for all public fields and properties.

### Node requirements

Only [object nodes](/configuration/concepts-and-basics/settings-nodes/object-nodes.md) are supported.

### Related pages

{% content-ref url="/pages/-M6UQlGKGPuVt1P3lsHf" %}
[Binding nodes to models](/configuration/concepts-and-basics/binding-nodes-to-models.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M6UVw-tcUFzsLRNvSXL" %}
[Make settings required](/configuration/basic-scenarios/make-settings-required.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M6UW-PeGz8EnJbqznWP" %}
[Make settings secret](/configuration/basic-scenarios/make-settings-secret.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M6UWWOyfG6A6vZl8C9q" %}
[Use name aliases](/configuration/advanced-scenarios/use-name-aliases.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M6UWDHXU4zRDdfV5Lcl" %}
[Apply custom binders](/configuration/advanced-scenarios/apply-custom-binders.md)
{% endcontent-ref %}