topic How to return a FeatureLayer with QueuedTask.Run in ArcGIS Pro SDK Questions

How to return a FeatureLayer with QueuedTask.Run

Amadeus111 — Wed, 22 Dec 2021 16:27:03 GMT

I would like to refactor my code and implement a method instead of writing/copying the same code again again.

I check TOC whether a certain Layer exists. If TOC does not have it I create the FeatureLayer. I use this process a lot in my applications.

So, here is the method but it does not work

public Task<FeatureLayer> AddLayerToTOC(Uri layerUri, string layerName) { return QueuedTask.Run(() => { MainGridEnabled = false; FeatureLayer fLayer; TOCLayers = MapView.Active.Map.Layers; var TOCLayerNames = TOCLayers.Select(p => p.Name); if (TOCLayerNames.Contains(layerName) == false) { fLayer = LayerFactory.Instance.CreateFeatureLayer(layerUri, MapView.Active.Map, 0, layerName); } else { foreach (Layer layer in TOCLayers) { if (layer.Name == layerName) { fLayer = layer as FeatureLayer;; } } } MapView.Active.ZoomToSelected(); MainGridEnabled = true; return fLayer; }); }

I get CS0165: Use of unassigned local variable

Problem coming from else {} part because VS thinks fLayer not assigned but I will do that while application is running.

Is there a solution to this or another way of doing it?

Re: How to return a FeatureLayer with QueuedTask.Run

GKmieliauskas — Thu, 23 Dec 2021 06:08:05 GMT

Hi,

It is simple. Set it to null:

FeatureLayer fLayer = null;

Re: How to return a FeatureLayer with QueuedTask.Run

Amadeus111 — Thu, 23 Dec 2021 15:58:25 GMT

Hi @GKmieliauskas ,

I think I did not explain my situaton well. I don't want it to be null. I would like to return the fLayer to main thread either as a new layer or a Layer from the TOC. So, I can make queries, extract data, table etc.

Maybe, I should declare the fLayer as public and assign it after checking its existence.

Re: How to return a FeatureLayer with QueuedTask.Run

GKmieliauskas — Thu, 23 Dec 2021 16:35:19 GMT

Hi,

Your code is fine. But compiler thinks that there is one situation when your method AddLayerToTOC could return unassigned fLayer value. For example if your foreach cycle will not be executed. This is compiler problem, not yours. And workaround for this is to preassign fLayer value with null in line 7.

Re: How to return a FeatureLayer with QueuedTask.Run

Amadeus111 — Mon, 27 Dec 2021 12:31:52 GMT

@GKmieliauskas,

Thanks for the solution and detailed explanation, it worked very well. This will help me to reduce lotta repetition.