PostgreSQL and Blazor .Net Core 3.1 - npgsql

Question

Are there any resources on how to use the current version of Blazor (3.1) and PostgreSQL?
I've tried writing the simplest code, just to see whether it connects to the database but I get this error message: System.Net.Dns:GetHostByName is not supported on this platform
a button click would activate this code:
async void connection()
{
var connString = "Host=Server1;Username=postgres;Password=pass;Database=BlazorData";
try
{
await using var conn = new NpgsqlConnection(connString);
await conn.OpenAsync();
errcheck = "success";
}
catch (Exception ex)
{
errcheck = ex.Message;
}
}

Answer 1

I explain how I use it with entity framework. It might help you.
in startup.cs, ConfigureServices method have this
services.AddEntityFrameworkNpgsql().AddDbContext<ApplicationDbContext>(options =>
options.UseNpgsql(Configuration.GetConnectionString("DefaultConnection")));
You need two packages to be installed through nuget
Npgsql.EntityFrameworkCore.PostgreSQL
Npgsql.EntityFrameworkCore.PostgreSQL.Design
in appsetting.json make sure you have setup connection string correctly, below one is mine. Host can be localhost if database is in the same machine as the database
"DefaultConnection": "Host=192.168.16.240;Port=5432;Username=postgres;Password=mypassword;Database=mydatabase;"
That's basically it.
then define a application db context with your tables
public class ApplicationDbContext : DbContext
{
public ApplicationDbContext(DbContextOptions options) : base(options)
{
}
public DbSet<Room> Rooms { get; set; }
public DbSet<Meal> Meals { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
}
}
in package mangaer console
add-migration initial
update-database
you should see the tables created in PgAdmin.
and use your dbsets like usual c# lists. and remember to inject applicationdbcontext in the controllers you need it.

Answer 2

The error says you need to resolve the hostname by yourself. Either pass an IP address or use Dns.GetHostEntry
using System.Linq;
using System.Net;
using System.Net.Sockets;
...
async void connection()
{
var host = Dns.GetHostEntry("Server1");
var firstIpV4Address = host.AddressList.First(a => a.AddressFamily == AddressFamily.InterNetwork);
var connString = $"Host={firstIpV4Address};Username=postgres;Password=pass;Database=BlazorData";
try
{
await using var conn = new NpgsqlConnection(connString);
await conn.OpenAsync();
errcheck = "success";
}
catch (Exception ex)
{
errcheck = ex.Message;
}
}