NPoco with PostgreSQL

NPoco is a great micro-ORM, that makes it really easy to work with a database in .NET. I needed to use it with PostgreSQL, so here is the initial test I wrote. Nothing spectacular, I just thought another tutorial doesn't hurt and it might get you started quicker.

Preparing the Database

First of all we need to create a user and database for this tutorial.

The user in this tutorial is called philipp and the database is called sampledb, you'll need these values for the connection string in C#.

PS C:\Users\philipp> psql -U postgres
psql (9.4.1)
postgres=# CREATE USER philipp WITH PASSWORD 'test_pwd';
postgres=# CREATE DATABASE sampledb
postgres-#   WITH OWNER philipp;

Next we'll create the Schema.


And then the Tables.

CREATE TABLE sample.address (
    address_id SERIAL PRIMARY KEY,
    street TEXT NOT NULL,
    house_no TEXT NOT NULL,
    city TEXT NOT NULL  

CREATE TABLE sample.person (
    person_id SERIAL PRIMARY KEY,
    firstname TEXT NOT NULL,
    lastname TEXT NOT NULL,
    address_id INTEGER REFERENCES sample.address (address_id)


Now the C# side!

We create a new library project and install the required libraries with NuGet:

Install-Package NUnit
Install-Package Npgsql
Install-Package NPoco

Then we'll add a new App.config to the project, which registers Npgsql as a DbProvider and defines a connection string.

<?xml version="1.0" encoding="utf-8" ?>

      <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql Server" type="Npgsql.NpgsqlFactory, Npgsql" />

    <add name="ApplicationConnectionString" connectionString="Server=;Port=5432;Database=sampledb;User Id=philipp;Password=test_pwd;" providerName="Npgsql" />


And then we can write a Unit Test to work with NPoco. The test shows how to define the POCOs, their Mappers with the NPoco.FluentMappings and register them with the DatabaseFactory.

using NPoco;
using NPoco.FluentMappings;
using NUnit.Framework;

namespace NPoco.Postgresql.Test
    public class PostgresqlNPocoTest
        public class Person
            public int PersonId { get; set; }
            public int AddressId { get; set; }
            public string FirstName { get; set; }
            public string LastName { get; set; }
            public int Age { get; set; }

            public override string ToString()
                return string.Format("Person, PersonId: {0}, FirstName: {1}, LastName: {2}, Age: {3}",
                    PersonId, FirstName, LastName, Age);

        public class Address
            public int AddressId { get; set; }
            public string Street { get; set; }
            public string HouseNo { get; set; }
            public string City { get; set; }

            public override string ToString()
                return string.Format("Address, AddressId: {0}, Street: {1}, HouseNo: {2}, City: {3}",
                    AddressId, Street, HouseNo, City);

        public class PersonMap : Map<Person>
            public PersonMap()
                PrimaryKey(p => p.PersonId, autoIncrement: true)
                .Columns(x =>
                    x.Column(p => p.PersonId).WithName("person_id");
                    x.Column(p => p.AddressId).WithName("address_id");
                    x.Column(p => p.FirstName).WithName("firstname");
                    x.Column(p => p.LastName).WithName("lastname");
                    x.Column(p => p.Age).WithName("age");

        public class AddressMap : Map<Address>
            public AddressMap()
                PrimaryKey(a => a.AddressId, autoIncrement: true)
                .Columns(x =>
                    x.Column(a => a.AddressId).WithName("address_id");
                    x.Column(a => a.Street).WithName("street");
                    x.Column(a => a.HouseNo).WithName("house_no");
                    x.Column(a => a.City).WithName("city");

        private DatabaseFactory databaseFactory;

        public void SetUp()
            DatabaseFactoryConfigOptions options = new DatabaseFactoryConfigOptions();

            options.Database = () => new Database("ApplicationConnectionString");
            options.PocoDataFactory = FluentMappingConfiguration.Configure(new PersonMap(), new AddressMap());

            databaseFactory = new DatabaseFactory(options);

        public void InsertAndQueryPersonTest()
            using (var db = databaseFactory.GetDatabase())
                using (var tran = db.GetTransaction())
                    // Clean existing items:
                    db.Execute("delete from sample.address");
                    db.Execute("delete from sample.person");

                    // Insert data:
                    var address = new Address()
                        Street = "Fakestreet",
                        HouseNo = "123",
                        City = "Faketown"

                    var person = new Person()
                        FirstName = "Philipp",
                        LastName = "Wagner",
                        Age = 10,
                        AddressId = address.AddressId

                    // Query data:
                    Person resultPerson = db.SingleById<Person>(person.PersonId);
                    Address resultAddress = db.SingleById<Address>(address.AddressId);

                    // Check data:
                    Assert.AreEqual(person.FirstName, resultPerson.FirstName);
                    Assert.AreEqual(person.LastName, resultPerson.LastName);
                    Assert.AreEqual(person.Age, resultPerson.Age);
                    Assert.AreEqual(address.AddressId, resultPerson.AddressId);

                    Assert.AreEqual(address.Street, resultAddress.Street);
                    Assert.AreEqual(address.HouseNo, resultAddress.HouseNo);
                    Assert.AreEqual(address.City, resultAddress.City);

And that's it! NPoco provides a lot more functionality of course, for more examples see the NPoco wiki.

How to contribute

One of the easiest ways to contribute is to participate in discussions. You can also contribute by submitting pull requests.

General feedback and discussions?

Do you have questions or feedback on this article? Please create an issue on the GitHub issue tracker.

Something is wrong or missing?

There may be something wrong or missing in this article. If you want to help fixing it, then please make a Pull Request to this file on GitHub.