AdditionalValidationAttributes package adds a few validation attributes to collection of attributes from System.ComponentModel.DataAnnotations namespace that are often required when for example validating request objects in asp.net

NonDefaultValueAttribute

class Class1
{
    [NonDefaultValue]
    public TimeSpan ValueType { get; set; }

    [NonDefaultValue]
    public string ReferenceType { get; set; }
}

For classes NonDefaultValueAttribute works same as RequiredAttribute. For structs it ensures that the value is not equal to default value for this type

GreaterThanAttribute

class Class1
{
    [GreaterThan(nameof(FromDate))]
    public DateTime ToDate { get; set; }

    public DateTime FromDate { get; set; }
}

The GreaterThanAttribute works with types that implement IComparable. The attribute ensures that the property marked with it is greater than other property specified in attribute constructor.

It's possible to enable 'greater or equal' comparison by setting property GreaterOrEqual of the attribute: [GreaterThan(nameof(FromDate), GreaterOrEqual = true)]