How can I add validations to print my own error message-CodePudding

I am creating a customer model for my API and I've set my 'Name' and 'Email' fields as required. But when we leave those fields empty while creating a new customer, we got a built-in error from EF core , instead I want to show my own error message...how can I do that.

I've tried to add validations by code in my post method but It doesn't work...can anyone help me with that?...Thanks in advance

CodePudding user response：

If you want to do simple validation: Fluent Validation

public class UserRegisterValidator : AbstractValidator<User>
{
    public UserRegisterValidator()
    {
        RuleFor(r => r.email).NotEmpty().WithMessage("Email address cannot be empty.");
       .
       .
       .
    }
}

When adding a new user

UserRegisterValidator v = new UserRegisterValidator();
ValidationResult result = v.Validate(usr);

if (!result.IsValid) return StatusCode(StatusCodes.Status400BadRequest, result.Errors); //Returns the specified error message
if (result.IsValid)
{
   //If there is no error, the necessary actions are here
}

CodePudding user response：

If you want to use server side validation you can specify the error message in validation tags. For example:

 public class Movie
{
    public int ID { get; set; }

    [Required(ErrorMessage = "Name is required")]
    public string Name{ get; set; }
}

Then you can also add some DetailsProvider to get better details when calling the api:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers(options =>
{
    options.ModelMetadataDetailsProviders.Add(new NewtonsoftJsonValidationMetadataProvider());
}).AddNewtonsoftJson();

Validation in front end has some other scenarios. Take a look at https://learn.microsoft.com/en-us/aspnet/core/mvc/models/validation?view=aspnetcore-7.0