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Copilot backlog handling: Fix authorId → author route parameter name mismatch in custom-model-binding article #36793

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23 changes: 12 additions & 11 deletions aspnetcore/mvc/advanced/custom-model-binding.md
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---
title: Custom Model Binding in ASP.NET Core
ai-usage: ai-assisted
author: tdykstra
description: Learn how model binding allows controller actions to work directly with model types in ASP.NET Core.
ms.author: tdykstra
ms.date: 04/03/2024
ms.date: 02/23/2026
uid: mvc/advanced/custom-model-binding
---
# Custom Model Binding in ASP.NET Core
Expand Down Expand Up @@ -59,15 +60,15 @@ The following example shows how to use `ByteArrayModelBinder` to convert a base6

[!code-csharp[](custom-model-binding/samples/3.x/CustomModelBindingSample/Controllers/ImageController.cs?name=snippet_Post)]

You can POST a base64-encoded string to the previous api method using a tool like [curl](https://curl.haxx.se/).
You can POST a base64-encoded string to the previous API method using a tool like [curl](https://curl.haxx.se/).

As long as the binder can bind request data to appropriately named properties or arguments, model binding will succeed. The following example shows how to use `ByteArrayModelBinder` with a view model:

[!code-csharp[](custom-model-binding/samples/3.x/CustomModelBindingSample/Controllers/ImageController.cs?name=snippet_SaveProfile&highlight=2)]

## Custom model binder sample

In this section we'll implement a custom model binder that:
In this section, we'll implement a custom model binder that:

* Converts incoming request data into strongly typed key arguments.
* Uses Entity Framework Core to fetch the associated entity.
Expand All @@ -79,12 +80,12 @@ The following sample uses the `ModelBinder` attribute on the `Author` model:

In the preceding code, the `ModelBinder` attribute specifies the type of `IModelBinder` that should be used to bind `Author` action parameters.

The following `AuthorEntityBinder` class binds an `Author` parameter by fetching the entity from a data source using Entity Framework Core and an `authorId`:
The following `AuthorEntityBinder` class binds an `Author` parameter by using the `author` route value to fetch the entity from a data source with Entity Framework Core:

[!code-csharp[](custom-model-binding/samples/3.x/CustomModelBindingSample/Binders/AuthorEntityBinder.cs?name=snippet_Class)]

> [!NOTE]
> The preceding `AuthorEntityBinder` class is intended to illustrate a custom model binder. The class isn't intended to illustrate best practices for a lookup scenario. For lookup, bind the `authorId` and query the database in an action method. This approach separates model binding failures from `NotFound` cases.
> The preceding `AuthorEntityBinder` class is intended to illustrate a custom model binder. The class isn't intended to illustrate best practices for a lookup scenario. For lookup, bind the `author` parameter directly and query the database in an action method. This approach separates model binding failures from `NotFound` cases.

The following code shows how to use the `AuthorEntityBinder` in an action method:

Expand All @@ -94,7 +95,7 @@ The `ModelBinder` attribute can be used to apply the `AuthorEntityBinder` to par

[!code-csharp[](custom-model-binding/samples/3.x/CustomModelBindingSample/Controllers/BoundAuthorsController.cs?name=snippet_GetById&highlight=2)]

In this example, since the name of the argument isn't the default `authorId`, it's specified on the parameter using the `ModelBinder` attribute. Both the controller and action method are simplified compared to looking up the entity in the action method. The logic to fetch the author using Entity Framework Core is moved to the model binder. This can be a considerable simplification when you have several methods that bind to the `Author` model.
In this example, since the route parameter name (`id`) doesn't match the action method parameter name (`author`), the `Name` property on the `ModelBinder` attribute is used to specify which route value to bind. Both the controller and action method are simplified compared to looking up the entity in the action method. The logic to fetch the author using Entity Framework Core is moved to the model binder. This can be a considerable simplification when you have several methods that bind to the `Author` model.

You can apply the `ModelBinder` attribute to individual model properties (such as on a viewmodel) or to action method parameters to specify a certain model binder or model name for just that type or action.

Expand All @@ -104,7 +105,7 @@ Instead of applying an attribute, you can implement `IModelBinderProvider`. This

[!code-csharp[](custom-model-binding/samples/3.x/CustomModelBindingSample/Binders/AuthorEntityBinderProvider.cs?highlight=17-20)]

> Note:
> [!NOTE]
> The preceding code returns a `BinderTypeModelBinder`. `BinderTypeModelBinder` acts as a factory for model binders and provides dependency injection (DI). The `AuthorEntityBinder` requires DI to access EF Core. Use `BinderTypeModelBinder` if your model binder requires services from DI.

To use a custom model binder provider, add it in `ConfigureServices`:
Expand Down Expand Up @@ -200,12 +201,12 @@ The following sample uses the `ModelBinder` attribute on the `Author` model:

In the preceding code, the `ModelBinder` attribute specifies the type of `IModelBinder` that should be used to bind `Author` action parameters.

The following `AuthorEntityBinder` class binds an `Author` parameter by fetching the entity from a data source using Entity Framework Core and an `authorId`:
The following `AuthorEntityBinder` class binds an `Author` parameter by fetching the entity from a data source using Entity Framework Core and an `author` route value:

[!code-csharp[](custom-model-binding/samples/2.x/CustomModelBindingSample/Binders/AuthorEntityBinder.cs?name=demo)]

> [!NOTE]
> The preceding `AuthorEntityBinder` class is intended to illustrate a custom model binder. The class isn't intended to illustrate best practices for a lookup scenario. For lookup, bind the `authorId` and query the database in an action method. This approach separates model binding failures from `NotFound` cases.
> The preceding `AuthorEntityBinder` class is intended to illustrate a custom model binder. The class isn't intended to illustrate best practices for a lookup scenario. For lookup, bind the `author` parameter directly and query the database in an action method. This approach separates model binding failures from `NotFound` cases.

The following code shows how to use the `AuthorEntityBinder` in an action method:

Expand All @@ -215,7 +216,7 @@ The `ModelBinder` attribute can be used to apply the `AuthorEntityBinder` to par

[!code-csharp[](custom-model-binding/samples/2.x/CustomModelBindingSample/Controllers/BoundAuthorsController.cs?name=demo1&highlight=2)]

In this example, since the name of the argument isn't the default `authorId`, it's specified on the parameter using the `ModelBinder` attribute. Both the controller and action method are simplified compared to looking up the entity in the action method. The logic to fetch the author using Entity Framework Core is moved to the model binder. This can be a considerable simplification when you have several methods that bind to the `Author` model.
In this example, since the route parameter name (`id`) doesn't match the action method parameter name (`author`), the `Name` property on the `ModelBinder` attribute is used to specify which route value to bind. Both the controller and action method are simplified compared to looking up the entity in the action method. The logic to fetch the author using Entity Framework Core is moved to the model binder. This can be a considerable simplification when you have several methods that bind to the `Author` model.

You can apply the `ModelBinder` attribute to individual model properties (such as on a viewmodel) or to action method parameters to specify a certain model binder or model name for just that type or action.

Expand All @@ -225,7 +226,7 @@ Instead of applying an attribute, you can implement `IModelBinderProvider`. This

[!code-csharp[](custom-model-binding/samples/2.x/CustomModelBindingSample/Binders/AuthorEntityBinderProvider.cs?highlight=17-20)]

> Note:
> [!NOTE]
> The preceding code returns a `BinderTypeModelBinder`. `BinderTypeModelBinder` acts as a factory for model binders and provides dependency injection (DI). The `AuthorEntityBinder` requires DI to access EF Core. Use `BinderTypeModelBinder` if your model binder requires services from DI.

To use a custom model binder provider, add it in `ConfigureServices`:
Expand Down