ASP.NET Core MVC: Model binding scenarios for nested complex types when using custom model binder
I'm trying to implement Quick question that's been bugging me - I'm currently working on an ASP.NET Core 6.0 MVC application, and I've implemented a custom model binder for a complex type that includes nested objects. However, I'm working with an scenario where the model binding fails for the nested properties, and I keep getting an behavior stating `The parameter 'SomeNestedModel' is required but was not provided.` I've confirmed that the incoming request has the necessary data in JSON format. Here's the custom model binder I created: ```csharp public class ComplexTypeModelBinder : IModelBinder { public Task BindModelAsync(ModelBindingContext bindingContext) { if (bindingContext == null) throw new ArgumentNullException(nameof(bindingContext)); var json = bindingContext.ValueProvider.GetValue(bindingContext.ModelName).FirstValue; if (string.IsNullOrEmpty(json)) return Task.CompletedTask; var model = JsonConvert.DeserializeObject<ComplexType>(json); bindingContext.Result = ModelBindingResult.Success(model); return Task.CompletedTask; } } ``` I've registered this model binder in the `Startup.cs` file: ```csharp services.AddControllers(options => { options.ModelBinderProviders.Insert(0, new ComplexTypeModelBinderProvider()); }); ``` And here’s the POCO class structure for my model: ```csharp public class ComplexType { public string Name { get; set; } public SomeNestedModel NestedModel { get; set; } } public class SomeNestedModel { public int Id { get; set; } public string Description { get; set; } } ``` When I make a POST request with the following JSON body: ```json { "Name": "Test", "NestedModel": { "Id": 1, "Description": "A nested model" } } ``` I see that the main property `Name` is being populated correctly, but `NestedModel` remains null. I've tried debugging and logging the incoming JSON string in the model binder, and it appears to be correct. I've also ensured that the JSON property names match the model property names. Is there something I'm missing in how I handle nested objects in my custom model binder? Any pointers on what I might be doing wrong or how to debug this further would be greatly appreciated! Thanks in advance! The stack includes C# and several other technologies. Am I missing something obvious?