Set a constraint for minimum int value

Question

I am using the Repository pattern. I have a entity called Product and I want to set the minimum value for price to avoid zero prices. Is it possible to create it in a EntitytypeConfiguration class?

My product configuration class

 public class ProductConfiguration : EntityTypeConfiguration<Product>
 {
    public PlanProductConfiguration(string schema = "dbo")
    {
        ToTable(schema + ".Product");
        HasKey(x => new { x.IdProduct });

        Property(x => x.Price).HasColumnName("flt_price")
                              .IsRequired()
                              .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
   }
}

Unfortunately Fluent API support only MaxLength

abatishchev
– abatishchev

2015-02-21 20:56:05 +00:00
Commented Feb 21, 2015 at 20:56 — abatishchev
– abatishchev, Commented Feb 21, 2015 at 20:56

Community · Accepted Answer · 2017-05-23 11:54:43Z

7

If you want that constraint, you can't apply it via EF configurations, but you can apply it using the check see here on the database directly, or you can apply data annotations on the model see this SO post

Something like:

[Range(0M, Double.MaxValue)]
public double Price { get; set; }

However that won't make a difference if you are using a view model, as those validations are only applied on ASP.NET object creation(generally when creating an instance from a web request into a controller), so when you create an instance you don't have to obey the attributes, so if you want to firmly validate it you need to apply a custom getter and setter rather than auto-properties, something like:

public class Product
{
    private double _price;

    [Range(0M, Double.MaxValue)]
    public double Price {
        get {
           return _price;
        }
        set {
            if (value <= 0M) {
                throw new ArgumentOutOfRangeException("value",
                        "The value must be greater than 0.0");
            }
            _price = value;
        }
    }
}

This will work fine in EF, so long as you don't have invalid data in the database.

edited May 23, 2017 at 11:54

CommunityBot

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answered Feb 21, 2015 at 20:09

tophallen

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4 Comments

Rodrigão Over a year ago

thanks! for the answer. The problem with data annotations is because I can't add other references in Domain Projects (that contains the entities). I gonna put the annotations in view model and the constraint directly in database. Thanks!

abatishchev Over a year ago

@Rodrigão: What's wrong with referencing System.Data.DataAnnotations.dll?

Rodrigão Over a year ago

Hi @abatishchev, in my domain layer, that contains the entities, I don't think that is a best practice reference anything but System. I think i going to do the Colin way and tell the result. Thanks!

abatishchev Over a year ago

From conservative point of view, you can reference nothing but BCL DLLs. So you're fine. But actually you can reference anything you need to achieve your goals. It won't violate no principles or practices.

abatishchev · Accepted Answer · 2015-02-22 22:31:42Z

3

Rather than attributes-based validation I recommend to use Fluent Validation which:

uses expressive lambda expressions
can be kept in other assembly than the models
doesn't polute POCOs with unrelated code

answered Feb 22, 2015 at 22:31

abatishchev

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Comments

Colin · Accepted Answer · 2015-02-22 09:47:23Z

2

For server side validation, implement IValidatableObject on your entity. For client-side validation, if you are using MVC, add the data annotation to your view model. And to add a database constraint, add the check constraint by calling the Sql() method in a migration.

answered Feb 22, 2015 at 9:47

Colin

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