Ignore property on model property [closed]

Question

How can I ignore a property on my model using dapper/dapper extensions/dapper rainbow or any

of those dapper libraries?

Ibnsina

For Insert<Person>(person). person has kind of computed property. Which does not belong to the database. – Ibnsina

Since non of the answers below provide a solution for a Dapper.Rainbow based project, I am adding this comment. Dapper Rainbow has an IgnoreProperty Attribute that can be used. Your POCO class has to reference Dapper.Rainbow.{SQL} and then you can use [IgnoreProperty(true)] for properties that you wish to exclude – Pederasty

Related for Dapper.Contrib: https://mcmap.net/q/501476/-what-39-s-the-difference-between-computed-and-write-false-attributes/5779732 – Flambeau

Answer 1

Dapper creator Sam Saffron has addressed this requirement in response to another SO user's questions here. Check it out.

Also, if you want to use the Dapper Extensions library that Sam has mentioned in his answer, you can get it from Github or via Nuget.

Here's an example of ignoring properties from the Library's Test Project.

using System;
using System.Collections.Generic;
using DapperExtensions.Mapper;

namespace DapperExtensions.Test.Data
{
    public class Person
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public DateTime DateCreated { get; set; }
        public bool Active { get; set; }
        public IEnumerable<Phone> Phones { get; private set; }
    }

    public class Phone
    {
        public int Id { get; set; }
        public string Value { get; set; }
    }

    public class PersonMapper : ClassMapper<Person>
    {
        public PersonMapper()
        {
            Table("Person");
            Map(m => m.Phones).Ignore();
            AutoMap();
        }
    }
}

Uphroe

Where/When do you instantiate the PersonMapper class ? Is dapper extensions looking for Mapper class by taking the entityname + "Mapper" string and trying to instantiate it? – Ibnsina

Yes, I believe the AutoMapper feature of Dapper Extensions looks for singular entity name + "Mapper" suffix to automap fields to ignore, fields with different names etc. In other words, I think (haven't tried it) you should be ok with just defining this PersonMapper class and ignoring the fields you want to ignore from the POCO. See the documentation here: github.com/tmsmith/Dapper-Extensions/wiki/AutoClassMapper – Uphroe

Fine it worked for me. My XXXMapper class has the same namespace. – Ibnsina

Answer 2

Dapper.Contrib has built-in support for marking a column as computed: add ComputedAttribute to allow support for computed columns on Insert. Here's how it works:

class MyModel
{
  public string Property1 { get; set; }

  [Computed]
  public int ComputedProperty { get; set; }
}

Properties marked with the Computed attribute will be ignored on inserts.

Angstrom

There is also [Write(false)] attribute. Can anyone tell what is the difference between [Computed] and [Write(false)]? – Aborticide

@Aborticide my best guess is that they were added at different times by different people who may not have been aware of the other. I added the Computed attribute and wasn't aware of any Write attribute at the time. – Angstrom

They mean something different in my opinion - [Computed] means "this column is in the database but is a Computed column" but [Write(false)] means "this column is not in the database" – Reuven

For details about [Write(false)] and [Computed], refer to this question. – Flambeau

Answer 3

In my case I used Dapper.Contrib.
Using [Write(false)] attribute on any property should solve the problem. Some also suggest using [Computed] attribute.

public class Person
{        
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }

    [Write(false)]
    public IEnumerable<Email> Emails { get; }
}

Tacheometer

Answer 4

You can design a base class without the computed property and use that for your inserts.

  class BasePerson
    {
      public String Name {get;set;}
    }

    class Person: BasePerson
    {
     public String ComputedProperty {get;set;}
    }

    Insert<BasePerson>(person);

Gonzales

Answer 5

For those not wanting to include DapperExtensions, DatabaseGenerated from the standard System.ComponentModel.DataAnnotations.Schema can be used also.

[DatabaseGenerated(DatabaseGeneratedOption.Computed)]

Tosch

This solution wont works with Dapper 1.50.2, on .NET CORE – Olvera

This didn't work for Insert/Update in Dapper.Contrib – Xavierxaviera

Using standard annotations as opposed to custom attributes should be the preferred choice for Dapper.Contrib – Briton