---
title: Filters
slug: cms-12/docs/filtering
createdAt: 2026-08-10T15:55:54.000Z
---

Filters narrow down search results, limiting a free-text search for books to a specific category or for database-like queries.

Search requests consist primarily of queries and filters. Queries and filters are similar. Filters perform better but do not affect scoring (sorting by relevance).

The .NET client API supports most filter types supported by the REST API and a fluent API for common filtering operations.

Assume a `BlogPost` class with a `Title` string property. The following code finds `BlogPosts` titled *Find*.

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Title.Match("Find"));
```

The `Search<TSource>` method returns an instance of `ITypeSearch<TSource>`, which acts as a builder class for a search request. Using the `Filter` extension method, you can add a filter to the search request by supplying an expression that returns an instance of the `Filter` class. The client API has several extension methods for value types and strings that return filters, such as the `Match` method above.

## Group filters

You can group filters using Boolean operators. For example, the following code finds blog posts titled *Find* or *Search*.

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Title.Match("Find") 
             | x.Title.Match("Search"));
```

Assuming the `BlogPost` class has a `Tag` property, the following code finds blog posts titled *Search* and tagged with *Find*, or titled *Find* (with no requirements for tags).

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => (x.Title.Match("Search")
              & x.Tags.Match("Find")) 
              | x.Title.Match("Find"));
```

## Call filter multiple times

You can call the `filter` method numerous times, which is useful at runtime if you determine the filters you want to apply, such as filters that depend on user input. For example, you can modify the first part of the filter expression above.

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Title.Match("Search"))
  .Filter(x => x.Tags.Match("Find"));
```

## OrFilter method

If you invoke the `Filter` method multiple times, the latter invocations' filters are combined with previous invocations' filters using **AND**. To combine them using **OR**, use the following code.

```csharp
var searchQuery = client.Search<BlogPost>()
  .Filter(x => x.Title.Match("Search"))
  .Filter(x => x.Tags.Match("Find"))
  .OrFilter(x.Title.Match("Find"));
```

If the `OrFilter` method is called *before* the `Filter` method, it is the same as calling the `Filter` method, because there is no existing filter to **OR** group it.

## Complex and dynamically created filters

Sometimes, the `Filter` and `OrFilter` methods are not enough. For example, you build complex search queries dynamically at runtime based on user input. While the methods can handle most scenarios at compile time, creating multiple grouped `Orfilters` at runtime is tricky and results in complex code. To build filters without regard to other filters and apply them to a search query, using the `IClient` extension method `BuildFilter`.

The `BuildFilter` method requires a generic type parameter to which you apply the filter. The method returns an object of type `FilterBuilder`. The `FilterBuilder` class has **And** and **Or** methods, which you use to add filter expressions like the `Filter` and `OrFilter` methods. The `FilterBuilder` class is implicitly convertible to the Filter class so that you can pass instances of it as arguments to the `Filter` and `OrFilter` methods and in filter expressions.

For example, you manage a restaurant search that uses two variables: cuisines and countries of type `IEnumerable<string>`. Each may be null, but if not, you want to add a filter so that search results return only restaurants matching those cuisines or countries. Use the `BuildFilter` method to accomplish this.

```csharp
var q = ...some search string

ITypeSearch<Restaurant> query = client.Search<Restaurant>().For(q);

if (cuisines != null) {
  var cuisineFilter = client.BuildFilter<Restaurant>();
  foreach(var cuisine in cuisines) {
    cuisineFilter = cuisineFilter.Or(x => x.Cuisine.Match(cuisine));
  }
  query = query.Filter(cuisineFilter);
}

if (countries != null) {
  var countryFilter = client.BuildFilter<Restaurant>();
  foreach(var country in countries) {
    countryFilter = countryFilter.Or(x => x.Country.Match(country));
  }
  query = query.Filter(countryFilter);
}

var results = query.GetResult();
```

## Filter methods

When filtering with the `Filter` method, you provide an expression that returns a filter. To do so, use extension methods for properties that return filters. The above examples used the `Match` extension method, but several other methods exist.

- Filter methods for:
  - [Boolean](docId\:UL33FjJnx0TM18ZyVmcjV) fields
  - [Complex objects](docId\:vO4vD6rbm4t2IYoH8NAUj)
  - [DateTime](docId\:SW7EJUR7Tudig8s96bdye) fields
  - [Enum](docId\:CX5e-YzpuGWkCnZ-l1bsR) fields
  - [Filter and FilterHits](docId:52m5agH56jJB19hIJJdxk)
  - [Numerical](docId:4FJBKdeoqVEvVsSo4G5-U) fields (int, int?, double etc)
  - [Strings](docId\:aS_hldF60vSbojglxrHxz)

You can also create [custom extension methods to enhance the filtering functionality](docId\:nBd6BhbtBYbI4lnbsJIPh).