> 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/basic-scenarios/make-settings-required.md).

# Make settings required

**Requires**: [abstractions module](/configuration/modules/abstractions.md).

By default all settings are optional; that is, absence of relevant data in the [source](/configuration/concepts-and-basics/configuration-sources.md) results in default values during [binding](/configuration/concepts-and-basics/binding-nodes-to-models.md) and does not produce errors. 

Some parts of configuration may be crucial to the application to the point that it's pointless to start without them being initialized. These fields and properties should be annotated with `[Required]` attribute:

```
class MySettings 
{
    [Required]
    public string DbConnectionString { get; }
    
    [Required]
    public MySecrets Secrets { get; }
}

class MySecrets 
{
    public string ApiKey { get; }
    public string Login { get; }
    public string Password { get; }
}
```

```
provider.Get<MySettings>(); // will throw if DbConnectionString or Secrets are not initialized 
```

###

### Changing defaults

Default behavior can be inverted in the scope of a type with `[RequiredByDefault]` attribute. Individual fields and properties can then be made optional with `[Optional]` attribute:

```
[RequiredByDefault]
class MySettings 
{
    [Optional]
    public TimeSpan Timeout { get; } = TimeSpan.FromSeconds(30);
}
```

###

### Related pages

{% content-ref url="/pages/-M6UVVWxjimC0yLfXc\_P" %}
[Obtain settings from provider](/configuration/basic-scenarios/obtain-settings-from-provider.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M6UVXzWRFlbId1t7QdO" %}
[Observe settings via provider](/configuration/basic-scenarios/observe-settings-via-provider.md)
{% endcontent-ref %}

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