A simple validatable model class.

ValidatableModel.cs

/// <summary>
/// A simple Model with validation logic built within it. 
/// Another approach of validation besides &quot; Data Annotations &quot; is to implement IValidatableObject interface.
/// </summary>
public class User : IValidatableObject
{
    public int Age { get; set; }

    public string Name { get; set; }

    public override IEnumerable<ValidationResult> Validate(ValidationContext context)
    {
        if (string.IsNullOrWhiteSpace(Name))
        {
            yield return new ValidationResult("Name cannot be empty.", new[] { "Name" });
        }

        if (Age > 100 || Age < 1)
        {
            yield return new ValidationResult("Age is invalid", new[] { "Age" });
        }

        if (Name.Split(' ').Length > 5)
        {
            yield return new ValidationResult("Name appears to be improper.", new[] { "Name" });
        }
    }
}