topic Re: Save graphics overlays? in .NET Maps SDK Questions

Save graphics overlays?

JonShuler — Fri, 28 Jun 2019 20:11:17 GMT

We would like to save the graphics overlays on a map and allow a user to add them back to a map at a later time. I did not see any functionality in the SDK for persisting the overlays. Without writing a lot of custom code, is it possible to save the overlays or even the complete map with the overlays?

Re: Save graphics overlays?

PreetiMaske — Mon, 01 Jul 2019 20:21:19 GMT

Graphics overlays allow graphics with multiple geometries and have no schema and hence can't be stored/persisted.

I am not completely sure of your workflow but seems like what you are trying to achieve might be possible by FeatureCollection.

Re: Save graphics overlays?

JonShuler — Mon, 01 Jul 2019 21:01:42 GMT

We are using the API to sketch shapes (polygon, point, etc) on the map. I found that the the Graphics object has a ToJson() for the geometry and symbol data so looking into using that. I will also look into FeatureCollection.

Re: Save graphics overlays?

JoeHershman — Sat, 11 Dec 2021 23:07:45 GMT

I think it would be pretty straight forward to just build out your own json array for each element using the .ToJson methods. Something like...

// Save to file
JArray array = new JArray();
foreach (var graphic in overlay.Graphics)
{
	JProperty geometry = new JProperty("geometry", graphic.Geometry.ToJson());
	JProperty symbol = new JProperty("symbol", graphic.Symbol.ToJson());
	JObject jObject = new JObject(geometry, symbol);

	array.Add(jObject);
}

StreamWriter sw = new StreamWriter("D:\\outfile.json");
JsonWriter writer = new JsonTextWriter(sw);
array.WriteTo(writer);
writer.Close();


//read back in
StreamReader reader = new StreamReader("D:\\outfile.json");
string json = reader.ReadToEnd();
JArray array = JArray.Parse(json);


foreach (var d in array.OfType<JObject>())
{
	string geo = d["geometry"].ToString();
	string sym = d["symbol"].ToString();

	var graph = new Graphic(Geometry.FromJson(geo), Symbol.FromJson(sym));

	overlay.Graphics.Add(graph);
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Save graphics overlays?

JoeHershman — Sat, 11 Dec 2021 23:07:48 GMT

You could make it really clean and roll your own ToJson

public static class OverlayExtension
{
	public static string ToJson(this GraphicsOverlay overlay)
	{
		JArray array = new JArray();
		foreach (var graphic in overlay.Graphics)
		{
			JProperty geometry = new JProperty("geometry", graphic.Geometry.ToJson());
			JProperty symbol = new JProperty("symbol", graphic.Symbol.ToJson());
			JObject jObject = new JObject(geometry, symbol);

			array.Add(jObject);
		}

		return array.ToString();
	}

	public static void FromJson(this GraphicsOverlay overlay, string json)
	{
		JArray array = JArray.Parse(json);
		foreach (var jObject in array.OfType<JObject>())
		{
			string geometry = jObject["geometry"].ToString();
			string symbol = jObject["symbol"].ToString();

			var graphic = new Graphic(Geometry.FromJson(geometry), Symbol.FromJson(symbol));

			overlay.Graphics.Add(graphic);
		}
	}
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Then in code

string json = EditGraphicsOverlay.ToJson();
//Write to file

//read from file
EditGraphicsOverlay.FromJson(json);‍‍‍‍‍‍‍‍‍‍