I am writing an ArcMap Add-In to combine multiple shapefiles and then run some custom python scripts on the resulting shapefile. However I cannot seem to get the Geoprocessor working to run the FeatureToLine tool. I am using the ArcGIS SDK 10.4 for .NET.

private void Button5_Click(object sender, EventArgs e)
        Geoprocessor gp = new Geoprocessor();
        gp.OverwriteOutput = true;

            FeatureToLine FTLTool = new FeatureToLine();

            List<string> inputs = new List<string>();

            string[] ins = new string[] { @"D:\\Code projects\\Network-WZRD\\Network Wzrd\\Data\\Centerlines\\Roadway\\Delaware.shp", 
                @"D:\\Code projects\\Network-WZRD\\Network Wzrd\\Data\\Centerlines\\Trails\\Trails.shp" };

            FTLTool.in_features = ins;
            FTLTool.out_feature_class = @"D:\\Code projects\\Network-WZRD\\Network Wzrd\\atestout.shp";
            ITrackCancel pTrackCancel = new CancelTracker();
            pTrackCancel.CancelOnKeyPress = true;

            gp.Execute(FTLTool, pTrackCancel);
        catch(Exception ex)
            MessageBox.Show("Error\nAn error occured while attempting to merge shapefiles.\n" + ex.Message);

    }//button5_Click -- Final Load

I know I am incorrectly inputing my shapefiles. But I couldn't find any examples of tools that used multiple inputs in the In_Feature field. I get a general error when it gets to execute the tool

Error HRESULT E_FAIL has been returned from a call to a COM component

The questions I have are: How can I input multiple shapefiles into the tool? Does the output need to be an existing shapefile object within the code, or can it just be a path to where I would like the resulting shapefile to be put?

EDIT: I tried Hornbydd's suggestion, and used the exact example in the sample code and got the same error code.

    public void ExampleGPUsingMultipleInputs()

        // Initialize the geoprocessor.
        Geoprocessor GP = new Geoprocessor();

        // Initialize the Union tool.
        Union uniontool = new Union();

        // List all feature classes in the workspace.
        GP.SetEnvironmentValue("workspace", @"D:\Code projects\Network-WZRD\Network Wzrd\Data\Centerlines\Trail");
        IGpEnumList fcColl = GP.ListFeatureClasses("*", "", "");

        // Create a StringBuilder object and add the feature classes as a semicolon-delimited list.
        StringBuilder sb = new StringBuilder();
        string inputfeatures = fcColl.Next();

        while (inputfeatures != "")
            sb.AppendFormat("{0};", inputfeatures);
            inputfeatures = fcColl.Next();

        // Execute the Union tool with multiple inputs creating landuse.shp.
        uniontool.in_features = sb.ToString();
        uniontool.out_feature_class = "landuse.shp";
        GP.Execute(uniontool, null);


1 Answer 1


I suspect the error is related to how you set your input features. Have a look at How to use multiple inputs, it gives examples in c# and vb.

  • I used the code from the example you gave (I just changed the directories to ones populated with 2 shapefiles) and got the same result: Exception thrown: 'System.Runtime.InteropServices.COMException' in ESRI.ArcGIS.Geoprocessor.dll
    – Zooloo10
    Commented Jun 29, 2016 at 14:26
  • 1
    Solved it. the union tool doesnt accept shape files with polyLines. But the feature to line does and it worked! Using a semicolon delineated list for the inputs like: FTLTool.in_features = @"D:\Code projects\Trail\Trails.shp;D:\Code projects\Trail\Trails2.shp;";
    – Zooloo10
    Commented Jun 29, 2016 at 15:43

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