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[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public class RequireNonDefaultAttribute : ValidationAttribute
{
    public RequireNonDefaultAttribute()
        : base("The {0} field requires a non-default value.")
    {
    }

    /// <summary>
    /// Override of <see cref="ValidationAttribute.IsValid(object)"/>
    /// </summary>
    /// <param name="value">The value to test</param>
    /// <returns><c>false</c> if the <paramref name="value"/> is equal the default value of an instance of its own type.</returns>
    /// <remarks>Is meant for use with primitive types or structs like DateTime, Guid, etc. Specifically ignores null values so that it can be combined with RequiredAttribute. Should not be used with Strings.</remarks>
    /// <example>
    /// //Allows you to effectively mark the field as required with out having to resort to Guid? and [Required] and then having to deal with SomeId.GetValueOrDefault() everywhere (and then test for Guid.Empty)
    /// [RequireNonDefault] 
    /// public Guid SomeId { get; set;}
    /// 
    /// //Enforces validation that requires the field beexplicitly provided, AND not be 0
    /// //Similar to [RequireNonDefault] int, except that using [Required] will add the client side validation (JS) to ensure a value is provided. I don't have client side validation for [RequireNonDefault] yet
    /// [Required][RequireNonDefault] 
    /// public int? SomeId { get; set;}
    /// 
    /// //Lets the field be optional, but if it IS provided, it can't be 0
    /// [RequireNonDefault]
    /// public decimal? Price { get; set;}
    /// 
    /// </example>
    public override bool IsValid(object value)
    {
        return value != null && !Equals(value, Activator.CreateInstance(value.GetType()));
    }
}