42 lines
1.6 KiB
Markdown
42 lines
1.6 KiB
Markdown
---
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title: "ASP0004: Do not use action results with route handlers"
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description: "Learn about analysis rule ASP0004: Do not use action results with route handlers"
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author: captainsafia
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monikerRange: '>= aspnetcore-6.0'
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ms.author: riande
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ms.date: 10/21/2021
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no-loc: [Home, Privacy, Kestrel, appsettings.json, "ASP.NET Core Identity", cookie, Cookie, Blazor, "Blazor Server", "Blazor WebAssembly", "Identity", "Let's Encrypt", Razor, SignalR]
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uid: diagnostics/asp0004
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---
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# ASP0004: Do not use action results with route handlers
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| | Value |
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| **Rule ID** |ASP0004|
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| **Category** |Usage|
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| **Fix is breaking or non-breaking** |Non-breaking|
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## Cause
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A route handler delegate returns a value that implements <xref:Microsoft.AspNetCore.Mvc.IActionResult>.
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## Rule description
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Route handler endpoints do not support executing MVC's `IActionResult` instances. Returning an `IActionResult` that doesn't implement `IResult` results in serializing the result instance rather than executing the result.
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```csharp
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app.MapGet("/todos/{id}", (int id) => new JsonResult(new Todo { .. }));
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```
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## How to fix violations
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To fix a violation of this rule, make sure that endpoint's route handler returns an <xref:Microsoft.AspNetCore.Http.IResult> type by using the <xref:Microsoft.AspNetCore.Http.Results> extension methods.
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```csharp
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app.MapGet("/todos/{id}", (int id) => Results.Json(new Todo { .. }));
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```
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## When to suppress warnings
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Do ***not*** suppress a warning from this rule. Returning an `IActionResult` that doesn't implement `IResult` results in serializing the result instance rather than executing the result.
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