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How to use a constructor from a Action model?

I am learning Dependency Injection.
How can I make my "UserCreate" model to use the custom constructor I set when it is being used as a parameter on controller action? I want to pass the UserContext to my UserCreate model.
My action:
[HttpPost]
public JsonResult Post(UserCreate model)
{
var user = _repository.GetByUserName(model.Email);
if (user != null)
{
this.ModelState.AddModelError(nameof(model.Email), "Email already registered!");
}
else
{
if (ModelState.IsValid)
{
var userModel = _mapper.Map<User>(model);
_repository.Add(userModel);
_repository.SaveChanges();
return Json(new { success = "true" });
}
}
return Json(new { success = "false", errors = this.ModelErrors(this.ModelState) });
}
My Model
public class UserCreate : BaseModel
{
private readonly IUserRepo repo;
public UserCreate(UserContext context) : base(context){
repo = new UserRepository(context);
}
public UserCreate():base() { }
[Required]
[MaxLength(100)]
public string Email { get; set; }
[Required]
[MaxLength(30)]
public string Password { get; set; }
[Required]
[MaxLength(30)]
public string FirstName { get; set; }
[Required]
[MaxLength(30)]
public string MiddleName { get; set; }
[Required]
[MaxLength(30)]
public string LastName { get; set; }
[Required]
public int Age { get; set; }
[Required]
public DateTime Birthday { get; set; }
[Required]
[MaxLength(250)]
public string Adddress { get; set; }
public DateTime Created { get { return DateTime.Now; } }
}
I've set it on startup:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<UserContext>(opt => opt.UseSqlServer
(Configuration.GetConnectionString("Dev")));
services.AddControllers();
services.AddScoped<IUserRepo, UserRepository>();
services.AddScoped<ICardRepo, CardRepository>();
services.AddScoped<IUserContext, UserContext>();
services.AddScoped<TransactCreate, TransactCreate>();
services.AddSingleton<UserCreate>(x =>
new UserCreate(x.GetRequiredService<UserContext>()));
I have set the Addsingleton on startup however when i test my API, public UserCreate():base() { } constructor is called instead of the constructor with UserContext parameter. I am using netcore 3.1
the reason why I want do this is I to move my validations to model and i need to use UserContext from there.
Thanks!

I understand what you are asking, but please understand that your approach to this problem is very flawed. Your view model should absolutely know nothing about your repository.
In MVC, the Controller is responsible for handling HTTP requests (as well as model validation), and delegating actions to the rest of the application. The Model (UserCreate), should be a simple poco that only exists to transfer data from the client back to your controller. The controller should then delegate responsibility to the repository for handling the data.
Your controller should, instead, accept the repository via DI, and then send the UserCreate model through, after validating it. And your model, UserCreate, should 100% have a parameterless constructor, as the ModelBinder is going to build it up from the request.

however what I want to achieve is if I have multiple properties that i
need to validate from the database, i dont want to write them all in
my controller action. Can you recommend the right way to handle custom
validations?
According to your code and the previous discuss, I suppose you want to valid whether the entered value is exist in the database, if the value exist, display the error message, such as "Email already registered". If that is the case, it is better to use the [Remote] attribute:
Code as below:
[Remote(action: "VerifyEmail", controller: "Users")]
public string Email { get; set; }
and
[AcceptVerbs("GET", "POST")]
public IActionResult VerifyEmail(string email)
{
if (!_userService.VerifyEmail(email))
{
return Json($"Email {email} is already in use.");
}
return Json(true);
}
Besides, if you want to create custom validation, you can check this thread, then, in the Custom validation IsValid method, you could get the current dbcontext and check whether the entered data is valid or not. Code as below:
code in the model:
[Required(ErrorMessage ="Country is Required")]
public string Country { get; set; }
[RequiredIfHasState("Country", ErrorMessage ="State is Required")]
public string State { get; set; }
code in the custom valiation:
public class RequiredIfHasStateAttribute : ValidationAttribute
{
private readonly string _comparisonProperty;
public RequiredIfHasStateAttribute(string comparisonProperty)
{
_comparisonProperty = comparisonProperty;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
ErrorMessage = ErrorMessageString;
//get entered state value
var stateValue = (string)value;
var property = validationContext.ObjectType.GetProperty(_comparisonProperty);
if (property == null)
throw new ArgumentException("Property with this name not found");
//get the country value
var countryValue = (string)property.GetValue(validationContext.ObjectInstance);
//get the current dbcontext
var _context = (MvcMovieContext)validationContext.GetService(typeof(MvcMovieContext));
//query the database and check whether the country has state.
if (_context.Countries.Where(c => c.CountryCode == countryValue).Select(c => c).FirstOrDefault().HasState)
{
if(stateValue == null)
{
//if country has state and the state is null. return error message
return new ValidationResult(ErrorMessage);
}
else
{
//if country has state and the state is not found.
if(!_context.Countries.Where(c => c.CountryCode == countryValue).Any(c => c.States.Any(e => e.StateName == stateValue)))
{
return new ValidationResult("State not found");
}
}
}
return ValidationResult.Success;
}
}

How can I use validation in self property object in C#?

I'm developing a little ERP to my company and I crashed into a problem about validation:
I have self property object like:
public class Person
{
[Required]
public string Name { get; set; }
public int Phone { get; set; }
public bool HasContact { get; set; }
public Person Contact { get; set; }
}
If HasContact is false, I don`t want put a Contact. If is true, I want.
The problem is my ModelState never is Valid, because Name is Required and Contact self implement Person.
I would like to set condition if HasContact is true, my application try validate the Contact property. If is not, set Valid and execute controller correct.
Is it possible or am I crazy?

You should have your object implement IValidatableObject. It lets you implement your own validation logic so you can ignore properties as necessary (see this SO question).
Your code might be something like this:
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
var results = new List<ValidationResult>();
if (this.HasContact)
{
Validator.TryValidateProperty(this.Contact,
new ValidationContext(this, null, null) { MemberName = "Contact" },
results);
}
return results;
}

C# DataAnnotations validation does not work for list

I have following object
public class TestClass
{
[Required]
public int TestId { get; set; }
}
I validate using:
List<ValidationResult> results = new List<ValidationResult>();
var vc = new ValidationContext(data);
if (Validator.TryValidateObject(data, vc, results, true))
return;
This validates perfectly fine if data is of type TestClass but not when I pass list of TestClass items (List<TestClass>)
How can I validate the items withing a list without iterating?

TryValidateObject expects an object and not a list of. You have to write a helper class. Furthermore it even doesn't recursively check the Validation. See this SO question for more...

Usually I add the Validate method in the class that I need to validate, and I foreach the property that has a list of T.
For example:
public class ClassToValidate : IValidatableObject
{
// Property with a non-custom type
[Required(AllowEmptyStrings = false, ErrorMessage = "\"Language\" is required. It can not be empty or whitespace")]
public string Language { get; set; }
// Property with a custom type
public Source Source { get; set; }
// Property with a custom type list
public List<Streaming> StreamingList { get; set; } = new List<Streaming>();
// Validate method that you need to implement because of "IValidatableObject"
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
// The validation result that will be returned
List<ValidationResult> result = new List<ValidationResult>();
// Language doesn't need to be added in the Validate method because it isn't a custom object
// Custom single T object to be validated
Validator.TryValidateObject(Source, new ValidationContext(Source), result, true);
// Custom list<T> object to be validated
foreach (var streaming in StreamingList)
{
Validator.TryValidateObject(streaming, new ValidationContext(streaming), result, true);
}
return result;
}
}
public class Source
{
[Range(16, 192, ErrorMessage = "\"Bitrate\" must be between 16 and 192")]
public int? Bitrate { get; set; }
public string Codec { get; set; }
}
public class Streaming
{
[Required(AllowEmptyStrings = false, ErrorMessage = "\"Url\" can not be empty")]
public string Url { get; set; }
[Range(0, 1000, ErrorMessage = "\"Offset\" must be between 0 and 1000")]
public int Offset { get; set; }
}

Validating form when model is a collection of sub models

I've got a view which needs several models to work correctly. So, I created a model which is a collection of multiple (sub) models. This is the model.
public class PolicyDetail
{
public Policy Policy { get; set; }
public IEnumerable<Insured> Insureds { get; set; }
public IEnumerable<Risk> Risks { get; set; }
public IEnumerable<Construction> Constructions { get; set; }
}
And here's an example of what one of the sub models look like, which is an actual entity from the database:
public class Policy
{
[Key]
public int PolicyID { get; set; }
[DisplayName("Policy Number")]
public Guid PolicyNumber { get; set; }
[Required(ErrorMessage = "Please enter a valid Effective Date.")]
[DataType(DataType.DateTime)]
[DisplayName("Effective Date")]
[DisplayFormat(DataFormatString = "{0:MM/dd/yyyy}", ApplyFormatInEditMode = true)]
public DateTime EffDate { get; set; }
[Required(ErrorMessage = "Please enter a valid Expiration Date.")]
[DataType(DataType.DateTime)]
[DisplayName("Expiration Date")]
[DisplayFormat(DataFormatString = "{0:MM/dd/yyyy}", ApplyFormatInEditMode = true)]
public DateTime ExpDate { get; set; }
public Boolean IsActive { get; set; }
}
This was all working well, right up until I tried to submit a form with errors in it to test the validation. I should have seen this coming (maybe?) but because the actual model doesn't have any validation tags on it, it always passes the if (ModelState.IsValid) check. Is there some way to enforce, or inherit, all of the Data Annotations from the sub classes?
Or, am I going about this all wrong, using a model which is a collection of other models? The thing is, I want to be able to edit/add multiple db entities from the same view.
EDIT:
This article by Josh Carroll looks to be EXACTLY what I need. But when I implement it, I get a Null Object error. Here's what I'm doing:
public class PolicyDetail
{
[Required, ValidateObject]
public Policy Policy { get; set; }
public IEnumerable<Insured> Insureds { get; set; }
public IEnumerable<Risk> Risks { get; set; }
public IEnumerable<Construction> Constructions { get; set; }
}
Then in the override method he provides:
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var results = new List<ValidationResult>();
var context = new ValidationContext(value, null, null);
Validator.TryValidateObject(value, context, results, true);
if (results.Count != 0)
{
var compositeResults = new CompositeValidationResult(String.Format("Validation for {0} failed!", validationContext.DisplayName));
results.ForEach(compositeResults.AddResult);
return compositeResults;
}
return ValidationResult.Success;
}
}
the parameter "value" comes in null, so it errors on this line:
Validator.TryValidateObject(value, context, results, true);
Am I missing something? Doing something wrong?

You can manually call the validations on the sub-models using this: https://msdn.microsoft.com/en-us/library/dd411772.aspx
var context = new ValidationContext(model.Policy, serviceProvider: null, items: null);
var validationResults = new List<ValidationResult>();
bool isValid = Validator.TryValidateObject(model.Policy, context, validationResults, true);
You can then use the ModelState.AddModelError to build the response from that.
Definitely not the most elegant possible solution, but might be easier than rewriting what you have.

ASP.NET MVC: Custom Validation by DataAnnotation

I have a Model with 4 properties which are of type string. I know you can validate the length of a single property by using the StringLength annotation. However I want to validate the length of the 4 properties combined.
What is the MVC way to do this with data annotation?
I'm asking this because I'm new to MVC and want to do it the correct way before making my own solution.

You could write a custom validation attribute:
public class CombinedMinLengthAttribute: ValidationAttribute
{
public CombinedMinLengthAttribute(int minLength, params string[] propertyNames)
{
this.PropertyNames = propertyNames;
this.MinLength = minLength;
}
public string[] PropertyNames { get; private set; }
public int MinLength { get; private set; }
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var properties = this.PropertyNames.Select(validationContext.ObjectType.GetProperty);
var values = properties.Select(p => p.GetValue(validationContext.ObjectInstance, null)).OfType<string>();
var totalLength = values.Sum(x => x.Length) + Convert.ToString(value).Length;
if (totalLength < this.MinLength)
{
return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));
}
return null;
}
}
and then you might have a view model and decorate one of its properties with it:
public class MyViewModel
{
[CombinedMinLength(20, "Bar", "Baz", ErrorMessage = "The combined minimum length of the Foo, Bar and Baz properties should be longer than 20")]
public string Foo { get; set; }
public string Bar { get; set; }
public string Baz { get; set; }
}

Self validated model
Your model should implement an interface IValidatableObject. Put your validation code in Validate method:
public class MyModel : IValidatableObject
{
public string Title { get; set; }
public string Description { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (Title == null)
yield return new ValidationResult("*", new [] { nameof(Title) });
if (Description == null)
yield return new ValidationResult("*", new [] { nameof(Description) });
}
}
Please notice: this is a server-side validation. It doesn't work on client-side. You validation will be performed only after form submission.

ExpressiveAnnotations gives you such a possibility:
[Required]
[AssertThat("Length(FieldA) + Length(FieldB) + Length(FieldC) + Length(FieldD) > 50")]
public string FieldA { get; set; }

To improve Darin's answer, it can be bit shorter:
public class UniqueFileName : ValidationAttribute
{
private readonly NewsService _newsService = new NewsService();
public override bool IsValid(object value)
{
if (value == null) { return false; }
var file = (HttpPostedFile) value;
return _newsService.IsFileNameUnique(file.FileName);
}
}
Model:
[UniqueFileName(ErrorMessage = "This file name is not unique.")]
Do note that an error message is required, otherwise the error will be empty.

Background:
Model validations are required for ensuring that the received data we receive is valid and correct so that we can do the further processing with this data. We can validate a model in an action method. The built-in validation attributes are Compare, Range, RegularExpression, Required, StringLength. However we may have scenarios wherein we required validation attributes other than the built-in ones.
Custom Validation Attributes
public class EmployeeModel
{
[Required]
[UniqueEmailAddress]
public string EmailAddress {get;set;}
public string FirstName {get;set;}
public string LastName {get;set;}
public int OrganizationId {get;set;}
}
To create a custom validation attribute, you will have to derive this class from ValidationAttribute.
public class UniqueEmailAddress : ValidationAttribute
{
private IEmployeeRepository _employeeRepository;
[Inject]
public IEmployeeRepository EmployeeRepository
{
get { return _employeeRepository; }
set
{
_employeeRepository = value;
}
}
protected override ValidationResult IsValid(object value,
ValidationContext validationContext)
{
var model = (EmployeeModel)validationContext.ObjectInstance;
if(model.Field1 == null){
return new ValidationResult("Field1 is null");
}
if(model.Field2 == null){
return new ValidationResult("Field2 is null");
}
if(model.Field3 == null){
return new ValidationResult("Field3 is null");
}
return ValidationResult.Success;
}
}
Hope this helps. Cheers !
References
Code Project - Custom Validation Attribute in ASP.NET MVC3
Haacked - ASP.NET MVC 2 Custom Validation

A bit late to answer, but for who is searching.
You can easily do this by using an extra property with the data annotation:
public string foo { get; set; }
public string bar { get; set; }
[MinLength(20, ErrorMessage = "too short")]
public string foobar
{
get
{
return foo + bar;
}
}
That's all that is too it really. If you really want to display in a specific place the validation error as well, you can add this in your view:
#Html.ValidationMessage("foobar", "your combined text is too short")
doing this in the view can come in handy if you want to do localization.
Hope this helps!