Using Merge GeoProcess task in ArcGIS Engine with C#?

Question

Having the hardest time getting the correct syntax when adding layers as gp parameters to call the Merge_management GeoProcessing Task. Below is just one of MANY, MANY ways I have tried with no luck. Can anyone help?

I've successfully called many GeoProcessing tasks via code in ArcEngine, but this is the first one to take an array ( ie. [layer1,layer2,etc]) as one of the parameters.

Intial Attemp:

 public void RunMergeGeoProcess(ILayer SourceLayer1, ILayer SourceLayer2, string ResultFeatureClassName, string GeoDBAbsFileName)
 {
 IFeatureLayer featureLayerSource1 = (IFeatureLayer)SourceLayer1;
 IFeatureLayer featureLayerSource2 = (IFeatureLayer)SourceLayer2;
 _geoProcessor.SetEnvironmentValue("Workspace", GeoDBAbsFileName);
 //_gpParams.Add(featureLayerSource1);
 ////_gpParams.Add(featureLayerSource2);
 IWorkspace refWS = ((IDataset)featureLayerSource1.FeatureClass).Workspace;
 string dbPath = refWS.PathName;
 IDataset myDS1 = featureLayerSource1.FeatureClass as IDataset;
 string mysDS1 = dbPath + "\\" + myDS1.Name;
 IDataset myDS2 = featureLayerSource2.FeatureClass as IDataset;
 string mysDS2 = dbPath + "\\"+ myDS2.Name;
 string myResult = dbPath + "\\" + ResultFeatureClassName;
 string param1 = "[" + mysDS1 + ", " + mysDS2 + "]";
 _gpParams.Add(param1);
 _gpParams.Add(myResult);
 try
 {
 _geoProcessor.OverwriteOutput = true;
 _geoProcessor.Execute("Merge_management", _gpParams, null);
 //returnMessages(_geoProcessor);
 }
 catch (Exception ex)
 {
 MessageBox.Show("There was a GeoProcessing Error." + ex.ToString());
 returnMessages(_geoProcessor);
 }
 _gpParams.RemoveAll();
 }

Working Version:

 public void RunMergeGeoProcess(ILayer SourceLayer1, ILayer SourceLayer2, string ResultFeatureClassName, string GeoDBAbsFileName)
 {
 IFeatureLayer featureLayerSource1 = (IFeatureLayer)SourceLayer1;
 IFeatureLayer featureLayerSource2 = (IFeatureLayer)SourceLayer2;
 _geoProcessor.SetEnvironmentValue("Workspace", GeoDBAbsFileName);
 IWorkspace refWS = ((IDataset)featureLayerSource1.FeatureClass).Workspace;
 string dbPath = refWS.PathName;
 IDataset myDS1 = featureLayerSource1.FeatureClass as IDataset;
 string mysDS1 = dbPath + "\\" + myDS1.Name;
 IDataset myDS2 = featureLayerSource2.FeatureClass as IDataset;
 string mysDS2 = dbPath + "\\" + myDS2.Name;
 string myResult = dbPath + "\\" + ResultFeatureClassName;
 string param1 = mysDS2 + ";" + mysDS1 ;
 _gpParams.Add(param1);
 _gpParams.Add(myResult);
 try
 {
 _geoProcessor.OverwriteOutput = true;
 _geoProcessor.Execute("Merge_management", _gpParams, null);
 //returnMessages(_geoProcessor);
 }
 catch (Exception ex)
 {
 MessageBox.Show("There was a GeoProcessing Error during the Merge Operation." + ex.ToString());
 //returnMessages(_geoProcessor);
 }
 _gpParams.RemoveAll();
 }

Answer 1

You should be able to use a semicolon-delimited list for the input parameter. An example using the Intersect tool is below:

 private void Intersect(List<string> LayerNames, string OutputLayerLocation)
 {
 Intersect inter;
 StringBuilder sb;
 Geoprocessor gg;
 sb = new StringBuilder();
 foreach (string LayerName in LayerNames)
 {
 sb.Append(LayerName);
 sb.Append(";");
 }
 sb.Length--;
 inter = new Intersect();
 inter.in_features = sb.ToString();
 inter.out_feature_class = OutputLayerLocation;
 gg = new Geoprocessor();
 gg.OverwriteOutput = true;
 gg.ProgressChanged += new EventHandler<ESRI.ArcGIS.Geoprocessor.ProgressChangedEventArgs>(gg_ProgressChanged);
 gg.ToolExecuted += new EventHandler<ToolExecutedEventArgs>(gg_ToolExecuted);
 gg.MessagesCreated += new EventHandler<MessagesCreatedEventArgs>(gg_MessagesCreated);
 gg.ExecuteAsync(inter);
 }

• Nathanus: To put it simply, the tool does not want an array, but a list of paths split on semi-colons: "C:\\PathToShape1;C:\\PathToShape2;C:\\PathToShape3"
• Michael Todd: @Nathanus That's the odd part; all the documentation I've seen mentions an "array", so I struggled with this myself. (And thanks for making my message a bit clearer.)
• user3013: Thanks a TON!!!!! I could not find that syntax ANYWHERE. Now it is working, I just need to work on the field mappings (when they are unequal). Thanks SO much!!! I'll post my version of final code, when done
• Nathanus: I came from Arcpy scripting, so I simply assumed it wanted the same kind of input it used in Python. Blind luck that I was right. How I came to the conclusion that I should have used a semicolon string instead of the list it shows in the documentation I do not remember... :)
• Nathanus: @user3013 Don't forget to mark Michael's answer as correct (there should be a check mark under the vote count on the side). Glad to be of help.