ASP.NET Core 6: Data Annotations Validation optimization guide with Custom Model Binder
I'm learning this framework and I'm having trouble with I'm attempting to set up I'm relatively new to this, so bear with me... I'm working with an scenario where data annotations for model validation are not being triggered when using a custom model binder in my ASP.NET Core 6 Web API project. I've implemented a custom model binder for a complex object that includes several properties, and I expected the validation attributes (like `[Required]` and `[StringLength]`) on these properties to be validated automatically, but it seems like they are being bypassed. Here’s a simplified version of my model: ```csharp public class UserModel { [Required] [StringLength(50)] public string Name { get; set; } [Required] [EmailAddress] public string Email { get; set; } } ``` My custom model binder looks like this: ```csharp public class UserModelBinder : IModelBinder { public Task BindModelAsync(ModelBindingContext bindingContext) { var name = bindingContext.ValueProvider.GetValue("name").FirstValue; var email = bindingContext.ValueProvider.GetValue("email").FirstValue; var userModel = new UserModel { Name = name, Email = email }; bindingContext.Result = ModelBindingResult.Success(userModel); return Task.CompletedTask; } } ``` In my controller, I’m using this binder: ```csharp [HttpPost] public IActionResult CreateUser([ModelBinder(BinderType = typeof(UserModelBinder))] UserModel user) { if (!ModelState.IsValid) { return BadRequest(ModelState); } // Process the valid user model... } ``` When I submit a request with missing or invalid fields, `ModelState.IsValid` remains `true`, and I don't see any validation errors. I've tried explicitly calling `Validator.TryValidateObject` within the binder, but I’m unsure how to integrate that correctly. Any suggestions on how to make the validation work with my custom binder? I’ve already checked that the `AddMvc()` call in `Startup.cs` is properly configured to use data annotations validation. I’m using ASP.NET Core 6.0 with C#. Any help would be appreciated! My development environment is Ubuntu. Thanks in advance! I recently upgraded to C# stable. What's the correct way to implement this? The project is a mobile app built with C#. This is for a web app running on Windows 10.