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wadepickett merged 1 commit into from
Feb 27, 2026
Merged

Merge to Live #36813

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13 changes: 7 additions & 6 deletions aspnetcore/web-api/action-return-types.md
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---
title: Controller action return types in ASP.NET Core web API
ai-usage: ai-assisted
author: tdykstra
description: ActionResult vs IActionResult
monikerRange: '>= aspnetcore-3.1'
ms.author: tdykstra
ms.custom: mvc
ms.date: 6/20/2023
ms.date: 02/26/2026
uid: web-api/action-return-types
---
# Controller action return types in ASP.NET Core web API
Expand Down Expand Up @@ -37,7 +38,7 @@ When multiple return types are possible, it's common to mix an <xref:Microsoft.A

### Return IEnumerable\<T> or IAsyncEnumerable\<T>

See [Return `IEnumerable<T>` or `IAsyncEnumerable<T>`](/aspnet/core/fundamentals/best-practices#return-ienumerablet-or-iasyncenumerablet) for performance considerations.
See [Return `IEnumerable<T>` or `IAsyncEnumerable<T>`](xref:fundamentals/best-practices#return-ienumerablet-or-iasyncenumerablet) for performance considerations.

ASP.NET Core buffers the result of actions that return <xref:System.Collections.Generic.IEnumerable%601> before writing them to the response. Consider declaring the action signature's return type as <xref:System.Collections.Generic.IAsyncEnumerable%601> to guarantee asynchronous iteration. Ultimately, the iteration mode is based on the underlying concrete type being returned and the selected formatter affects how the result is processed:

Expand Down Expand Up @@ -97,7 +98,7 @@ If the [`[ApiController]`](xref:Microsoft.AspNetCore.Mvc.ApiControllerAttribute)

## ActionResult vs IActionResult

The following section compares `ActionResult` to `IActionResult`
The following section compares `ActionResult` to `IActionResult`.

### ActionResult\<T> type

Expand Down Expand Up @@ -144,12 +145,12 @@ In the preceding action:

## HttpResults type

In addition to the MVC-specific built-in result types (<xref:Microsoft.AspNetCore.Mvc.IActionResult> and [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult%601)), ASP.NET Core includes the [HttpResults](xref:Microsoft.AspNetCore.Http.HttpResults) types that can be used in both [Minimal APIs](/aspnet/core/fundamentals/minimal-apis) and Web API.
In addition to the MVC-specific built-in result types (<xref:Microsoft.AspNetCore.Mvc.IActionResult> and [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult%601)), ASP.NET Core includes the [HttpResults](xref:Microsoft.AspNetCore.Http.HttpResults) types that can be used in both [Minimal APIs](xref:fundamentals/minimal-apis) and Web API.

Different than the MVC-specific result types, the `HttpResults`:

* Are a results implementation that is processed by a call to [IResult.ExecuteAsync](xref:Microsoft.AspNetCore.Http.IResult.ExecuteAsync%2A).
* Does ***not*** leverage the configured [Formatters](/aspnet/core/web-api/advanced/formatting#format-specific-action-results). Not leveraging the configured formatters means:
* Does ***not*** leverage the configured [Formatters](xref:web-api/advanced/formatting#format-specific-action-results). Not leveraging the configured formatters means:

* Some features like `Content negotiation` aren't available.
* The produced `Content-Type` is decided by the `HttpResults` implementation.
Expand All @@ -160,7 +161,7 @@ The `HttpResults` can be useful when sharing code between Minimal APIs and Web A

The <xref:Microsoft.AspNetCore.Http.HttpResults> namespace contains classes that implement the <xref:Microsoft.AspNetCore.Http.IResult> interface. The `IResult` interface defines a contract that represents the result of an HTTP endpoint. The static [Results](<xref:Microsoft.AspNetCore.Http.Results>) class is used to create varying `IResult` objects that represent different types of responses.

The [Built-in results](/aspnet/core/fundamentals/minimal-apis#built-in-results) table shows the common result helpers.
The [Built-in results](xref:fundamentals/minimal-apis#built-in-results) table shows the common result helpers.

Consider the following code:

Expand Down
10 changes: 5 additions & 5 deletions aspnetcore/web-api/action-return-types/includes/action-return-types7.md
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ When multiple return types are possible, it's common to mix an <xref:Microsoft.A

### Return IEnumerable\<T> or IAsyncEnumerable\<T>

See [Return `IEnumerable<T>` or `IAsyncEnumerable<T>`](/aspnet/core/fundamentals/best-practices#return-ienumerablet-or-iasyncenumerablet) for performance considerations.
See [Return `IEnumerable<T>` or `IAsyncEnumerable<T>`](xref:fundamentals/best-practices#return-ienumerablet-or-iasyncenumerablet) for performance considerations.

ASP.NET Core buffers the result of actions that return <xref:System.Collections.Generic.IEnumerable%601> before writing them to the response. Consider declaring the action signature's return type as <xref:System.Collections.Generic.IAsyncEnumerable%601> to guarantee asynchronous iteration. Ultimately, the iteration mode is based on the underlying concrete type being returned and the selected formatter affects how the result is processed:

Expand Down Expand Up @@ -84,7 +84,7 @@ If the [`[ApiController]`](xref:Microsoft.AspNetCore.Mvc.ApiControllerAttribute)

## ActionResult vs IActionResult

The following section compares `ActionResult` to `IActionResult`
The following section compares `ActionResult` to `IActionResult`.

### ActionResult\<T> type

Expand Down Expand Up @@ -131,12 +131,12 @@ In the preceding action:

## HttpResults type

In addition to the MVC-specific built-in result types (<xref:Microsoft.AspNetCore.Mvc.IActionResult> and [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult%601)), ASP.NET Core includes the [HttpResults](xref:Microsoft.AspNetCore.Http.HttpResults) types that can be used in both [Minimal APIs](/aspnet/core/fundamentals/minimal-apis) and Web API.
In addition to the MVC-specific built-in result types (<xref:Microsoft.AspNetCore.Mvc.IActionResult> and [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult%601)), ASP.NET Core includes the [HttpResults](xref:Microsoft.AspNetCore.Http.HttpResults) types that can be used in both [Minimal APIs](xref:fundamentals/minimal-apis) and Web API.

Different than the MVC-specific result types, the `HttpResults`:

* Are a results implementation that is processed by a call to [IResult.ExecuteAsync](xref:Microsoft.AspNetCore.Http.IResult.ExecuteAsync%2A).
* Does ***not*** leverage the configured [Formatters](/aspnet/core/web-api/advanced/formatting#format-specific-action-results). Not leveraging the configured formatters means:
* Does ***not*** leverage the configured [Formatters](xref:web-api/advanced/formatting#format-specific-action-results). Not leveraging the configured formatters means:

* Some features like `Content negotiation` aren't available.
* The produced `Content-Type` is decided by the `HttpResults` implementation.
Expand Down Expand Up @@ -275,7 +275,7 @@ If the [`[ApiController]`](xref:Microsoft.AspNetCore.Mvc.ApiControllerAttribute)

## ActionResult vs IActionResult

The following section compares `ActionResult` to `IActionResult`
The following section compares `ActionResult` to `IActionResult`.

### ActionResult\<T> type

Expand Down