Spatial Queries in .NET with PostGIS and NetTopologySuite

Why PostGIS?

PostGIS extends PostgreSQL with 500+ spatial functions. Combined with NetTopologySuite, you get strongly-typed geometry in .NET.

Setup

builder.Services.AddDbContext<GisDbContext>(o =>
    o.UseNpgsql(conn, x => x.UseNetTopologySuite()));

Entity with Geometry

public class Site
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public Point Location { get; set; } = null!; // SRID 4326
}

Distance Query

var userPoint = new Point(72.8777, 19.0760) { SRID = 4326 };
var nearby = await db.Sites
    .Where(s => s.Location.Distance(userPoint) < 5000)
    .OrderBy(s => s.Location.Distance(userPoint))
    .ToListAsync();

Conclusion

NetTopologySuite + PostGIS is the most productive GIS stack for .NET developers. No raw SQL, full LINQ support.