# Assign sources to types

**Requires**: [main module](https://vostok.gitbook.io/configuration/modules/configuration).

When using [configuration providers](https://vostok.gitbook.io/configuration/concepts-and-basics/configuration-provider), **Get** and **Observe** method overloads without parameters require an explicit association of the model type with a [configuration source](https://vostok.gitbook.io/configuration/concepts-and-basics/configuration-sources).

```
// This simply won't work (no source defined):

provider.Get<MySettings>();
provider.Observe<MySettings>();
```

```
// This will work as expected:

provider.SetupSourceFor<MySettings>(new JsonFileSource("settings.json"));

provider.Get<MySettings>();
provider.Observe<MySettings>();
```

A source can only be assigned to a type before any **Get** or **Observe** calls are made for that type:

```
provider.SetupSourceFor<MySettings>(source1); // succeeds

provider.SetupSourceFor<MySettings>(source2); // succeeds, overwrites

provider.Get<MySettings>();

provider.SetupSourceFor<MySettings>(source3); // fails
```

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