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Export a feature layer to shapefile with clipping

sbayarri_gilytics

Hi everyone.

We need to export a feature layer in the map to a shapefile, but applying a clipping operation with a code-built polygon. The original layer must not be modified.

We've tried running the "analysis.Clip" tool. Unlike the old "arcpy.Clip_analysis", the ArcGIS Pro SDK version seems to require providing the clipping polygon (second GP value) as a FeatureLayer.

We think we need to either:

Make an in-memory FeatureLayer containing the Polygon.
Save my polygon to a temporary file whose path can be used as input for the analysis.Clip process.

We could find a way to do either one in C#. Maybe you can provide a sample or have other ideas. We would prefer not to create any intermediate visible layers in the Map.

Thanks!

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Accepted answers

CharlesMacleod

try this:

internal class Button1 : Button
  {
    protected async void OnClickClip()
    {
      var tool_name = "analysis.Clip";
      var extent = MapView.Active.Extent;
      var sel_layer = MapView.Active.Map.GetLayersAsFlattenedList()
                        .OfType<FeatureLayer>().FirstOrDefault(l => l.Name == "GreatLakes");
      if (sel_layer == null) return;

      var gdb = Project.Current.DefaultGeodatabasePath;
      var out_fc = System.IO.Path.Combine(gdb, "clipped_lakes_out");

      var val_array = await QueuedTask.Run(() =>
      {

        var rect = GeometryEngine.Instance.Scale(extent, extent.Center, 0.5, 0.5) as Envelope;
        var clip_poly = PolygonBuilderEx.CreatePolygon(rect, rect.SpatialReference);
        var geom = new List<object>() { clip_poly };
        return Geoprocessing.MakeValueArray(new object[] { sel_layer, geom, out_fc });

      });

      Geoprocessing.ExecuteToolAsync(tool_name, val_array,
        null, null, null, GPExecuteToolFlags.InheritGPOptions);
    }

    protected override void OnClick()
    {
      OnClickClip();
    }
  }

All comments

Richard Howe

A feature layer is a temporary construct within an ArcMap/Pro session, and that is absolutely the way I would go. Really easy to call in arcpy via the "Make Feature Layer" tool. There has always been a little bit of inconsistency in both ArcMap and ArcGIS Pro about which tools require Feature Layers as inputs, and while it's a little bit of a faff, it's realistically only a single extra line of code

sbayarri_gilytics

Thanks, Richard.

In the end, my solution is quite complex, but I don't see a shorter way. Basically:

It creates an empty feature class (shapefile) and opens it as a layer (clipLayer), so the clip polygon can be added to it.
It calls the Clip GP tool with this clip layer to do the clipping and save the resulting shapefile.

public static async Task<Layer> CreateLayerFromPolygon(string tempDirectory, Polygon clipArea)
        {
            GPExecuteToolFlags flags = GPExecuteToolFlags.GPThread;  // instruct the tool run non-blocking GPThread

            // Create empty feature class
            var valueArrayCreateFCArea = Geoprocessing.MakeValueArray(tempDirectory, "clip_area.shp", "POLYGON");
            IGPResult gpResult = await Geoprocessing.ExecuteToolAsync("management.CreateFeatureclass", valueArrayCreateFCArea, null, null, null, flags);
            if (!Utils.VerifyGPToolResult(gpResult))
                return null;

            // Load feature class as layer
            Uri clipAreaFile = new Uri(Path.Combine(tempDirectory, "clip_area.shp"));
            Layer clipLayer = null;
            await QueuedTask.Run(() =>
                clipLayer = LayerFactory.Instance.CreateLayer(clipAreaFile, Utils.getActiveMap())
            );
            if (clipLayer == null)
                return null;

            // Add clip area to clip layer
            var editOp = new EditOperation();
            editOp.Create(clipLayer, clipArea);
            if (!editOp.Execute())
                return null;

            return clipLayer;
        }

Layer clipLayer = await Utils.CreateLayerFromPolygon(tempDirectory, clipArea);
GPExecuteToolFlags flags = GPExecuteToolFlags.GPThread;

var valueArray = await QueuedTask.Run(() =>
{
    List<string> inlayers = new List<string>();
    inlayers.Add(layerNameToBeClipped);
    string outpath = Path.Combine(outShpDirectory, layerNameToBeClipped + ".shp");
    return Geoprocessing.MakeValueArray(inlayers, clipLayer, outpath);
});

IGPResult gpResult = await Geoprocessing.ExecuteToolAsync("analysis.Clip", valueArray, null, null, null, flags);

CharlesMacleod

try this:

internal class Button1 : Button
  {
    protected async void OnClickClip()
    {
      var tool_name = "analysis.Clip";
      var extent = MapView.Active.Extent;
      var sel_layer = MapView.Active.Map.GetLayersAsFlattenedList()
                        .OfType<FeatureLayer>().FirstOrDefault(l => l.Name == "GreatLakes");
      if (sel_layer == null) return;

      var gdb = Project.Current.DefaultGeodatabasePath;
      var out_fc = System.IO.Path.Combine(gdb, "clipped_lakes_out");

      var val_array = await QueuedTask.Run(() =>
      {

        var rect = GeometryEngine.Instance.Scale(extent, extent.Center, 0.5, 0.5) as Envelope;
        var clip_poly = PolygonBuilderEx.CreatePolygon(rect, rect.SpatialReference);
        var geom = new List<object>() { clip_poly };
        return Geoprocessing.MakeValueArray(new object[] { sel_layer, geom, out_fc });

      });

      Geoprocessing.ExecuteToolAsync(tool_name, val_array,
        null, null, null, GPExecuteToolFlags.InheritGPOptions);
    }

    protected override void OnClick()
    {
      OnClickClip();
    }
  }

sbayarri_gilytics

Thanks, Charles!! That's a much better solution 🙂

I just needed to pass my clip area to the GP as a List, like you do. I guess the docs could be more clear about accepting clip features as a list, but not a single feature. Anyway, thanks a lot!

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