How to put conditional Required Attribute into class property to work with WEB API?

Question

I just want to put conditional Required Attribute which is work with WEB API

Example

public sealed class EmployeeModel
{
      [Required]
      public int CategoryId{ get; set; }
      public string Email{ get; set; } // If CategoryId == 1 then it is required
}

I am using Model State validation via (ActionFilterAttribute)

score 54 · Accepted Answer · edited May 21 '20 at 14:12

54

You can implement your own ValidationAttribute. Perhaps something like this:

public class RequireWhenCategoryAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var employee = (EmployeeModel) validationContext.ObjectInstance;
        if (employee.CategoryId == 1)
            return ValidationResult.Success;

        var emailStr = value as string;
        return string.IsNullOrWhiteSpace(emailStr)
            ? new ValidationResult("Value is required.")
            : ValidationResult.Success;
    }
}

public sealed class EmployeeModel
{
    [Required]
    public int CategoryId { get; set; }
    [RequireWhenCategory]
    public string Email { get; set; } // If CategoryId == 1 then it is required
}

This is just a sample. It may have casting issues, and I'm not sure this is the best approach to solve this problem.

edited May 21 '20 at 14:12

Ian Kemp

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answered Dec 17 '13 at 19:05

vcsjones

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"*I'm not sure this is the best approach to solve this problem.*" What would be some other approaches to solve the problem? – Scott Chamberlain Dec 17 '13 at 19:08
@ScottChamberlain Excellent question! I don't know. I feel like this somehow is a leaky abstraction. The attribute doing the validation knows a lot about the model type, etc. Should this be done in via an attribute? It feels like the model knows too much about behavior and has lost a model's simplicity. Should the controller be doing it then? I'm still not sure. – vcsjones Dec 17 '13 at 19:13
3

@ vcsjones : It is a good approach, actually I want to avoid validation logic in controller, because that's required lots of changes (as per change requirement), which I don't want to do. – Shubhajyoti Ghosh Dec 18 '13 at 06:48
10

@ShubhajyotiGhosh, @ScottChamberlain: To save your time and gain some flexibility, instead of creating custom validation attributes for each specific case, take a look at [ExpressiveAnnotations](https://github.com/JaroslawWaliszko/ExpressiveAnnotations). By using it in this case, you can annotate `Email` field with the following attribute: `[RequiredIf("CategoryId == 1")]`. – jwaliszko Sep 03 '15 at 12:52
I don't understand whats wrong with this solution. @ScottChamberlain Its what I immediately thought if. I just prefer it to adding Modelstate errors in the controller if something is not set... – Andy Nov 05 '15 at 11:53
2

Actually this comment is wrong: If CategoryId == 1 then it is NOT required – bombek Mar 05 '20 at 10:30
1

Fanatastic answer. Saved my life! Thanks. – leighhydes Mar 08 '20 at 15:48

score 6 · Answer 2 · answered Jun 05 '19 at 14:43

Here's my 2 cents. It will give you a nice message like "AssigneeId is required for the current AssigneeType value Salesman" It works for enums too.

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
public class RequiredForAnyAttribute : ValidationAttribute
{
    /// <summary>
    /// Values of the <see cref="PropertyName"/> that will trigger the validation
    /// </summary>
    public string[] Values { get; set; }

    /// <summary>
    /// Independent property name
    /// </summary>
    public string PropertyName { get; set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var model = validationContext.ObjectInstance;
        if (model == null || Values == null)
        {
            return ValidationResult.Success;
        }

        var currentValue = model.GetType().GetProperty(PropertyName)?.GetValue(model, null)?.ToString();
        if (Values.Contains(currentValue) && value == null)
        {
            var propertyInfo = validationContext.ObjectType.GetProperty(validationContext.MemberName);
            return new ValidationResult($"{propertyInfo.Name} is required for the current {PropertyName} value {currentValue}");
        }
        return ValidationResult.Success;
    }
}

Use it like this

public class SaveModel {
    [Required]
    public AssigneeType? AssigneeType { get; set; }

    [RequiredForAny(Values = new[] { nameof(AssigneeType.Salesman) }, PropertyName = nameof(AssigneeType))]
    public Guid? AssigneeId { get; set; }
}

I copied your attribute, thanks for sharing :) – ilyas varol Dec 09 '22 at 13:21 — ilyas varol, Dec 09 '22 at 13:21

How to put conditional Required Attribute into class property to work with WEB API?

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