PropertyHandler

This attribute is used to signal a property handling operation on the class property. By having this attribute, the library compiler will automatically trigger the property handler Get() and Set() method during the serialization/deserialization and hydration process.

Let us say you had created a customized IPropertyHandler like below.

private class PersonAddressHandler : IPropertyHandler<string, Address>
{
    public Address Get(string input, PropertyHandlerGetOptions options)
    {
        return JsonConvert.Deserialize<Address>(input);
    }

    public string Set(Address input, PropertyHandlerSetOptions options)
    {
        return JsonConvert.Serialize(input);
    }
}

Then, you can use this attribute to mark the class property to use the PersonAddressHandler property handler during the transformation.

public class Person
{
    public long Id { get; set; }
    public string Name { get; set; }
    [PropertyHandler(typeof(PersonAddressHandler))]
    public Address Address { get; set; }
}

When you read the records from the database, the Address property is then filled by the value of the Address column that is being serialized as an actual class.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(10045);
    Console.WriteLine($"Name: {person.Name}, Address: {person.Address.Street}, {person.Address.Region}, {person.Address.Country} ({person.Address.ZipCode})")
}

The aim of this sample is to show that the property Address of the Person class is on type NVARCHAR(MAX) at the [dbo].[Person] table. In addition, if this attribute is present on the property, then it ignores the automatic conversion of TypeMapper and enumerations.