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Update action-return-types.md (#23271)

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---
title: Controller action return types in ASP.NET Core web API
author: rick-anderson
description: Learn about using the various controller action method return types in an ASP.NET Core web API.
description: IActionResult vs IActionResult
ms.author: scaddie
ms.custom: mvc
ms.date: 02/03/2020
@ -139,9 +139,13 @@ For example, the following model indicates that requests must include the `Name`
If the [`[ApiController]`](xref:Microsoft.AspNetCore.Mvc.ApiControllerAttribute) attribute in ASP.NET Core 2.1 or later is applied, model validation errors result in a 400 status code. For more information, see [Automatic HTTP 400 responses](xref:web-api/index#automatic-http-400-responses).
## ActionResult\<T> type
## ActionResult vs IActionResult
ASP.NET Core 2.1 introduced the [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult`1) return type for web API controller actions. It enables you to return a type deriving from <xref:Microsoft.AspNetCore.Mvc.ActionResult> or return a [specific type](#specific-type). `ActionResult<T>` offers the following benefits over the [IActionResult type](#iactionresult-type):
The following section compares `ActionResult` to `IActionResult`
### ActionResult\<T> type
ASP.NET Core includes [ActionResult\<T>](xref:Microsoft.AspNetCore.Mvc.ActionResult`1) return type for web API controller actions. It enables you to return a type deriving from <xref:Microsoft.AspNetCore.Mvc.ActionResult> or return a [specific type](#specific-type). `ActionResult<T>` offers the following benefits over the [IActionResult type](#iactionresult-type):
* The [`[ProducesResponseType]`](xref:Microsoft.AspNetCore.Mvc.ProducesResponseTypeAttribute) attribute's `Type` property can be excluded. For example, `[ProducesResponseType(200, Type = typeof(Product))]` is simplified to `[ProducesResponseType(200)]`. The action's expected return type is instead inferred from the `T` in `ActionResult<T>`.
* [Implicit cast operators](/dotnet/csharp/language-reference/keywords/implicit) support the conversion of both `T` and `ActionResult` to `ActionResult<T>`. `T` converts to <xref:Microsoft.AspNetCore.Mvc.ObjectResult>, which means `return new ObjectResult(T);` is simplified to `return T;`.