---
title: Complex objects
slug: cms-12/docs/complex-objects
docTags: 
createdAt: 2026-08-10T15:55:58.000Z
---

Use filters to narrow down search results, or use them for database-like queries.

The REST API and .NET client API support varying degrees of filtering on complex objects of different types. You can divide supported complex objects into the following types:

- Collections of native objects such as `IEnumerable<int>`.
- Complex objects that have properties of native objects and complex objects, for example, an `Author` class.
- Collections of complex objects, such as `IEnumerable<Author>`.

## Collection of native objects

The documentation covers the first type for each *native* type. For instance, if you want to know how to filter on a property of type `IEnumerable<string>`, see [Strings](docId\:aS_hldF60vSbojglxrHxz).

## Complex objects with properties of native objects

The second type, *complex objects*, such as a property of type `Author` is straightforward. You can filter on its native properties as if they were a part of the type you are searching for. For instance, to find blog posts authored by *Winston Churchill*, you could use the following code.

**Example:**

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Author.Name.Match("Winston Churchill"));
```

One might wonder what happens if the `Author` property is null. It does not throw an exception, contrary to LINQ. The filter does not match.

## Complex object collections

The final type of complex objects that you can filter is a *collection of complex objects*, such as `IEnumerable<Author>`. The .NET client API has a filter method named `MatchContained`, which you can use to filter on properties of native types in objects in collections. Imagine that the `BlogPost` class no longer has an `Author` property but instead an `Authors` property of type `IEnumerable<Author>`. Next, use the `MatchContained` method to find blog posts whose `Author` property contains an `Author` with a specific name.

**Example:**

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Authors.MatchContained(a => a.Name, "Winston Churchill"));
```

:::hint{type="info"}
**Not**
The `MatchContained` syntax is a bit different from other filtering methods. The first argument is an expression identifying the property that we want to filter on. The second argument is the value.
:::

Also, while the `MatchContained` method lets you filter on a single field in an object in a list, you cannot use it to express multiple conditions on the same object in the list. Use it to find blog posts with an author named *Winston Churchill* and an author with a specific email address. You cannot use it to find blog posts with an author's exact name and email address.