Spatial Data in .NET · TechBash 2026

Cold open

From database to dashboard

Spatial Data in .NET

SPATIAL DATA IN .NET

From database
to dashboard

Store the location, not just the coordinates.

Tim Purdum · dymaptic
TechBash 2026

41.3604° N75.6840° W

The job

A freezer is failing. Who can we send?

A repair company near Scranton dispatches technicians to customer jobs.

URGENT

Summit Sports Catering

Walk-in freezer
temperature alarm

Covers this address.
Available now.
Closest to the job.

Spatial data

A point is a location. A polygon is an area.

SQL Server can find what is inside an area and measure how far away it is.

POINT · JOBS AND TECHNICIANS

How far from the job?

POLYGON · SERVICE TERRITORIES

Inside this territory?

Spatial data

SQL Server has stored shapes since 2008

Mature, stable, and already in the database you use.

2008SQL SERVER 2008

geometry and geography column types

2012SQL SERVER 2012

Whole-globe shapes, AUTO_GRID spatial indexes, 48-bit precision

2012ENTITY FRAMEWORK 5

DbGeography, with SQL Server's types installed separately

2018EF CORE 2.2

NetTopologySuite Point and Polygon in your model

TODAYEF CORE 10 · SQL SERVER 2025

No spatial changes in the release notes since EF Core 7 in 2022

If you run SQL Server, you already have spatial types.

The app

Build a dispatch dashboard

01SQL SERVER

Store locations

02EF CORE

Find a technician

03API

Send the result

04BLAZOR

Show it on a map

Store

Use the geography Db type for latitude and longitude

THIS MAP

`geography`

Locations on Earth
Distance in meters with SRID 4326

FLAT COORDINATES

`geometry`

Floor plans and local grids
Distance in coordinate units

SRID 4326 identifies WGS 84, our longitude-and-latitude reference.

Store

Map C# shapes to SQL columns

NetTopologySuite provides the C# spatial types.

public Point Location { get; set; }
public Polygon Boundary { get; set; }

NETTOPOLOGYSUITE

Define the shapes

options.UseSqlServer(
  connectionString,
  sql => sql.UseNetTopologySuite());

EF CORE

Enable spatial support

Location geography NOT NULL
Boundary geography NOT NULL

SQL SERVER

Store the values

Store

How did this address become a point?

Geocode addresses as they are entered into your database.

ADDRESS

Summit Sports Catering

235 Montage Mountain Road
Moosic, Pennsylvania

GEOCODER

Geocoded coordinates

lon -75.683967
lat  41.360406

C# POINT

NetTopologySuite

new Point(-75.683967,
         41.360406)
{ SRID = 4326 }

SQL ROW

Jobs.Location

geography
POINT (-75.683967
  41.360406)

One customer record: an address becomes a queryable point.

Store

Where does a service territory come from?

Draw your own areas, or import boundaries you already have.

DRAWN

North Valley

Four vertices on a map

STORED RING

POLYGON ((-75.830000 41.352000,
  -75.610000 41.352000,
  -75.585000 41.500000,
  -75.835000 41.500000,
  -75.830000 41.352000))

Boundary geography · SRID 4326

QUERIED LATER

t.Boundary
  .Contains(job.Location)

The same shape every containment query tests

Drawn or imported, it becomes one stored ring.

Store

Point takes longitude first

NetTopologySuite: new Point(longitude, latitude)

World map with the swapped point in East Antarctica — SWAPPED`new Point(41.4, -75.7)`

Map with the correct point in Pennsylvania — CORRECT`new Point(-75.7, 41.4)`

Query

Which territory contains the job?

EF Core translates Contains into a SQL spatial test.

LINQ QUERY

List<TerritoryEntity> containingTerritories =
    await db.Territories
        .Where(t => t.Boundary.Contains(job.Location))
        .ToListAsync(cancellationToken);
TerritoryEntity? territory =
    containingTerritories.SingleOrDefault();

GENERATED SQL

SELECT [t].[Id], [t].[Name], [t].[Boundary]
FROM [Territories] AS [t]
WHERE [t].[Boundary].STContains(
  @jobLocation) = CAST(1 AS bit);

The job is in North Valley.

Query

Spatial query quirks

The seed data avoids all three situations.

Outside every territory

No match: the customer is outside coverage.

Inside two territories

Two matches: an explicit priority, or a review.

On a shared border

A deliberate boundary and ownership rule.

The query reports what the shapes are. Your application decides what that means.

Query

Who is available and closest?

Filter by territory and availability. Then order by distance.

LINQ

db.Technicians
  .Where(t => t.TerritoryId == territory.Id
    && t.IsAvailable)
  .OrderBy(t => t.Location.Distance(job.Location))
  .FirstOrDefaultAsync();

Nearest, unavailableMorgan Lee · 303 m
Nearest, wrong territoryRiley Chen · 1,129 m
Nearest matchJordan Alvarez · 5,688 m

GENERATED SQL

SELECT TOP(1) [t].[Id], [t].[Name], [t].[TerritoryId]
FROM [Technicians] AS [t]
WHERE [t].[TerritoryId] = @territory_Id
  AND [t].[IsAvailable] = CAST(1 AS bit)
ORDER BY [t].[Location].STDistance(@job_Location);

Query

What will the database do with this?

Predict the work before the next slide reveals it.

db.Technicians
  .Where(t => t.TerritoryId == territory.Id
    && t.IsAvailable)
  .OrderBy(t => t.Location.Distance(job.Location))
  .FirstOrDefaultAsync();

Rows readEvery row, or a shortcut?
The sortWho sorts, and how many rows?
The indexDoes one even get used?

Query

Sorting by distance can still scan every row

Prepared plan: 200,000 technicians

SQL Server execution plan showing a clustered index scan

Query

Use a spatial index to narrow the search

Find candidate cellsSkip unrelated areas
Check the shapesTest containment or distance

HAND-WRITTEN MIGRATION SQL

CREATE SPATIAL INDEX SIX_Territories_Boundary
  ON Territories(Boundary)
  USING GEOGRAPHY_AUTO_GRID;

Query

Add a distance filter to use the spatial index

45.3 km covers this company's service area.

SQL Server execution plan showing a spatial index seek

API

Send shapes to the map and a result to the app

MAP

`GeoJSON`

Territory boundaries
Technician locations

DISPATCH RESULT

`JSON`

North Valley
Jordan Alvarez
5,688 meters

API

GeoJSON pairs a shape with its properties

Geometry

Where to draw

Properties

What to label

{
  "type": "Feature",
  "geometry": {
    "type": "Point",
    "coordinates": [-75.683967, 41.360406]
  },
  "properties": { "name": "Summit Sports Catering" }
}

Coordinates use WGS 84, longitude first.

API

Follow a territory from the database to the map

One Minimal API endpoint turns EF Core rows into GeoJSON features.

1ENDPOINTApi/MapLayerEndpoints.cs

layers.MapGet("/territories", async (DispatchDbContext db,
    CancellationToken cancellationToken) =>
{
    List<Territory> territories = await db.Territories
        .OrderBy(t => t.Id)
        .ToListAsync(cancellationToken);
    return MapLayerFeatures.ForTerritories(territories);
});

2FEATURESMapLayerFeatures.cs

AttributesTable attributes = new()
{
    { "TerritoryId", territory.Id },
    { "Name", territory.Name }
};
collection.Add(
    new Feature(territory.Boundary, attributes));

3SERIALIZERProgram.cs

builder.Services.ConfigureHttpJsonOptions(options =>
    options.SerializerOptions.Converters.Add(
        new GeoJsonConverterFactory()));

4ON THE WIREGET /api/layers/territories

{ "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "geometry": { "type": "Polygon",
      "coordinates": [[[-75.83, 41.352], …]] },
    "properties": { "TerritoryId": 1,
                    "Name": "North Valley" } },
  … ] }

TerritoryId is a contract: the map's highlight filters on it.

API

Keep large maps quick to load

DATABASE

Keep full boundaries

REQUEST

Filter to the visible area

await db.Territories
  .Where(t => t.Boundary
    .Intersects(view))
  .ToListAsync();

DISPLAY

Simplify for this zoom

TopologyPreservingSimplifier
  .Simplify(boundary, meters);

Map

Show the dispatch result in Blazor

GeoBlazor adds maps and layers to Blazor.

LOAD

Territories and technicians

<GeoJSONLayer Url="@LayerSource.TerritoriesUrl" />
<GeoJSONLayer Url="@LayerSource.TechniciansUrl" />

SELECT

The customer's job

await graphicsLayer.Add(new Graphic(
    new Point(job.Longitude, job.Latitude),
    new SimpleMarkerSymbol(JobFill, 18)));

HIGHLIGHT

Territory and technician

<GeoJSONLayer Url="@LayerSource.TerritoriesUrl"
    DefinitionExpression="@($"TerritoryId = ${id}")"
    Opacity="0.55" />

DRAW

Route to the job

await graphicsLayer.Add(new Graphic(
    new Polyline([new MapPath(path)]),
    new SimpleLineSymbol(RouteColor, 4)));
await mapView.GoTo([routeGraphic]);

Map

Jordan is the closest available match

Spatial Dispatch dashboard with North Valley selected and Jordan Alvarez recommended

Map

Nearest by distance may take longer to drive

This demo selects a technician first, then requests a route.

SQL SERVER

Choose the technician

Geographic distance
Jordan · 5.7 km

ROUTING SERVICE

Draw the trip

Road routeConnector if routing fails

Map

Let a routing service rank by drive time

ArcGIS routing services answer the questions straight-line distance cannot.

CLOSEST FACILITY

Who gets to this job first?

Ranks up to 10 technicians per job by travel time, in one direct request.

SERVICE AREA

Where can a technician reach in 15 minutes?

Returns drive-time polygons, also called isochrones. GeoBlazor Pro wraps it as ServiceAreaService.

VEHICLE ROUTING PROBLEM

Who visits which jobs today, in what order?

Assigns a day's jobs to a fleet and orders each van's stops: the traveling salesman, solved as a service.

Let SQL Server shortlist the candidates. Pay for drive times on the shortlist.

Live demo

Send someone to fix the freezer

01SELECT

The urgent job

02FIND

North Valley

03RECOMMEND

Jordan · 5.7 km

04ASSIGN

Jordan to the job

Next steps

What if we use PostgreSQL?

PostGIS answers the same territory and nearest-technician questions.

SQL SERVER

options.UseSqlServer(
  connectionString,
  sql => sql.UseNetTopologySuite());

Boundary.STContains(job)
meters via geography

POSTGIS · NPGSQL

options.UseNpgsql(
  connectionString,
  sql => sql.UseNetTopologySuite());

ST_Contains(Boundary, job)
same NetTopologySuite LINQ

Carries over: the C# model, the LINQ shape, the GeoJSON pipeline.

Check first: PostGIS defaults to geometry — opt into geography for meter distances. Index with GiST. Confirm translation coverage.

Other engines: Azure SQL Database runs the SQL Server engine. SQLite stores shapes but translates few spatial methods.

Next steps

What if someone already publishes the spatial data?

The company keeps its boundaries in a GIS and serves them.

MAINTAIN

The GIS team draws territories

PUBLISH

A feature service on ArcGIS

CONSUME

Load it like any layer

MAP / DATA SERVICES

Boundaries and locations your app reads again and again. The dashboard's GeoJSON endpoint is one of these.

TRANSIENT SERVICES

Geocoding and routing, called per request — like this demo's single route call.

Next steps

How much map can I build in Blazor?

The dashboard already uses layers, graphics, selection, and events.

<MapView Longitude="@ViewLongitude"
         Latitude="@ViewLatitude" Zoom="@ViewZoom">
    <Map>
        <Basemap>
            <OpenStreetMapLayer />
        </Basemap>
        <GeoJSONLayer Url="@LayerSource.TerritoriesUrl"
                      Title="Service territories" />
        <GeoJSONLayer Url="@LayerSource.TechniciansUrl"
                      Title="Technicians" />
        <GraphicsLayer @ref="_graphicsLayer" Title="Dispatch" />
    </Map>
</MapView>

DispatchMap.razor · trimmed

IN THIS DEMO

A MapView with a GeoJSONLayer per data set
A GraphicsLayer draws the job, technician, and route
The dispatch result's territory ID drives the highlight

GOING FURTHER · PRO

Sketch widget: draw and edit territory boundaries
Feature forms and tables for GIS-style workflows
This demo already requires a Pro license

A published ArcGIS feature service can feed the same layers.

Takeaways

Add spatial queries to your .NET app

Store

SQL geography

Model

C# Point / Polygon

Query

Contains / Distance

Send

GeoJSON + result

Display

Blazor map

Takeaways

Check these in your own app

01

Coordinate order

Longitude first for our Point and GeoJSON.

02

Distance units

Meters for this geography data.

03

SQL translation

Check the generated query.

04

Index use

Inspect the execution plan.

Wrap

Spatial is just a data type.

Questions

Wrap

Questions

QR code that opens the write-up for this session. — WRITE-UP
Write-up and links
`timpurdum.dev/post/2026/10/15/techbash.html`

Feedback QR code
not added yet

FEEDBACK

Session feedback on Sessionize

Two minutes, and it decides whether this talk runs again.

Sample app: github.com/dymaptic/GeoBlazor-Samples · projects/SpatialDispatch

Appendix

Running the sample

GeoBlazor-Samples · projects/SpatialDispatch

CONFIGURE

SpatialDispatch/
  appsettings.Development.json.template
SpatialDispatch.Client/wwwroot/
  appsettings.Development.json.template

Copy each template without .template. The host's copy holds the connection string; the client's holds GeoBlazor:LicenseKey. Both are gitignored.

RUN

cd projects/SpatialDispatch
docker compose up -d
dotnet run --project SpatialDispatch

Startup waits for SQL Server, applies the migration, and seeds the data.

Needs: the .NET 10 SDK, Docker, and a GeoBlazor Pro license key. A free Core key won't load Pro.

Without a key: the map asks for one, but the dispatch answer, the candidates, and assignment still work.

Optional: on Windows, set ConnectionStrings__DispatchDatabase to LocalDB instead of running the container. An ArcGISApiKey adds road routing; without it, a dashed connector.

Appendix

Reproducing the index investigation

Scratch data behind the plans on slides 14 and 16

RANKING

WHERE [t].[Location].STDistance(@jobLocation)
  <= 45269
ORDER BY [t].[Location].STDistance(@jobLocation)

STDistance in WHERE and the first ORDER BY
200,000 → 13,211 rows read

CONTAINMENT

List<TerritoryEntity> matches = await db.Territories
    .Where(t => t.Boundary.Contains(job.Location))
    .ToListAsync(cancellationToken);
TerritoryEntity? territory = matches.SingleOrDefault();

SingleOrDefaultAsync emits TOP(2), which chose a scan
15,918 → 24 rows read

Scratch data: 200,000 technician points and 40,000 territory polygons, with the real columns, clustered primary keys, and GEOGRAPHY_AUTO_GRID indexes.

Setup traps: no clustered primary key raises error 12008. Script with sqlcmd -I, or CREATE SPATIAL INDEX fails with error 1934.

Your data: 45 km is the diagonal of this company's territories, not a general rule. Measure at your own row counts.

From databaseto dashboard

Summit Sports Catering

How far from the job?

Inside this territory?

Store locations

Find a technician

Send the result

Show it on a map

geography

geometry

Define the shapes

Enable spatial support

Store the values

Summit Sports Catering

Geocoded coordinates

NetTopologySuite

Jobs.Location

North Valley

Outside every territory

Inside two territories

On a shared border

GeoJSON

JSON

Geometry

Properties

Keep full boundaries

Filter to the visible area

Simplify for this zoom

Territories and technicians

The customer's job

Territory and technician

Route to the job

Choose the technician

Draw the trip

Who gets to this job first?

Where can a technician reach in 15 minutes?

Who visits which jobs today, in what order?

The urgent job

North Valley

Jordan · 5.7 km

Jordan to the job

The GIS team draws territories

A feature service on ArcGIS

Load it like any layer

Store

Model

Query

Send

Display

Coordinate order

Distance units

SQL translation

Index use

Write-up and links

Session feedback on Sessionize

From database
to dashboard

`geography`

`geometry`

`GeoJSON`

`JSON`