Selections boxes required at least 1 with Data Annotations

Question

In the model I have:

[Display(Name = "Exemplo 1")]
[Range(typeof(bool), "true", "true", ErrorMessage = "Erro, marcar como true")]
public bool Exemplo1 { get; set; }

[Display(Name = "Exemplo 2")]
public bool Exemplo2 { get; set; }

[Display(Name = "Exemplo 3")]
public bool Exemplo3 { get; set; }

In the view I have :

@Html.CheckBoxFor(model => model.Exemplo1, new { id = "toggle1", data_on = "Sim", data_off = "Não", data_toggle = "toggle", data_class = "fast", data_size = "mini", data_onstyle = "success", data_offstyle = "danger" })
@Html.ValidationMessageFor(model => model.Exemplo1, "", new { @class = "text-danger" })

@Html.CheckBoxFor(model => model.Exemplo2, new { id = "toggle2", data_on = "Sim", data_off = "Não", data_toggle = "toggle", data_class = "fast", data_size = "mini", data_onstyle = "success", data_offstyle = "danger" })

@Html.CheckBoxFor(model => model.Exemplo3, new { id = "toggle3", data_on = "Sim", data_off = "Não", data_toggle = "toggle", data_class = "fast", data_size = "mini", data_onstyle = "success", data_offstyle = "danger" })

I have a "Create" post button. By clicking "Create" button, show red warning when the 3 checkbox buttons is 3 false. Must be at least 1 true to process post.

How to do this using Data Annotations ?

Answer 1

What you want is a conditional validation. There are several ways to do this and some of them I will demonstrate below:

Interface Ivalidatableobject.

With it you can perform some extra checks on the Model. For your example, it would look something like this:

using System.ComponentModel.DataAnnotations;

public class MeuModel : IValidatableObject
{

    [Display(Name = "Exemplo 1")]
    [Range(typeof(bool), "true", "true", ErrorMessage = "Erro, marcar como true")]
    public bool Exemplo1 { get; set; }

    [Display(Name = "Exemplo 2")]
    public bool Exemplo2 { get; set; }

    [Display(Name = "Exemplo 3")]
    public bool Exemplo3 { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (Exemplo1 == false && Exemplo2 == false && Exemplo3 == false)
        {
            yield return new ValidationResult("Erro, marcar como true",
                         new[] { "Exemplo1", "Exemplo2", "Exemplo3" });
        }
    }
}

Where is new[] { "Exemplo1", "Exemplo2", "Exemplo3" }); will be the place where the validation message will be displayed, i.e., here: @Html.ValidationMessageFor(model => model.Exemplo1, "", new { @class = "text-danger" }). If you wish to display only the Example1 no need to add the other.

More details can be seen in this answer.

Expressive Annotations

This is a package with several custom attributes to suit various activities. Its use would look something like this:

[Display(Name = "Exemplo 1")]
[RequiredIf("Exemplo1 == false && Exemplo2 == false && Exemplo3 == false",
ErrorMessage = "Erro, marcar como true")]
public bool Exemplo1 { get; set; }

[Display(Name = "Exemplo 2")]
public bool Exemplo2 { get; set; }

[Display(Name = "Exemplo 3")]
public bool Exemplo3 { get; set; }

More details in this answer.

Another option would be to check the controller and add an error in the ModelState or you yourself develop your own Customattribute.