I've always went the route of using the managed assemblies when using the Geoprocessor in .NET. Here's an example of how I run the Dissolve tool, using inputs representing either feature classes or feature layers (either as path names or as ArcObjects) and all the associated functions to execute the Geoprocessor and return a feature class.
Dim GP As ESRI.ArcGIS.Geoprocessor.Geoprocessor 'set in the beginning of the code
Friend Function DissolveDataset(ByVal InputName As Object, ByVal DissolveField As String, ByVal StatsFields As String, ByVal OutputName As String) As ESRI.ArcGIS.Geodatabase.IFeatureClass
Dim DissolveDS As New ESRI.ArcGIS.DataManagementTools.Dissolve
Dim Result As ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2
Try
Using releaser As New ESRI.ArcGIS.ADF.ComReleaser
releaser.ManageLifetime(DissolveDS)
DissolveDS.in_features = InputName
DissolveDS.dissolve_field = DissolveField
DissolveDS.statistics_fields = StatsFields
DissolveDS.out_feature_class = OutputName
Result = RunTool(DissolveDS, Nothing)
If Result Is Nothing Then
System.Windows.Forms.MessageBox.Show("Could not dissolve dataset")
Return Nothing
End If
Return ReturnObjectfromResult(Result, "Feature Class")
End Using
Catch ex As Exception
System.Windows.Forms.MessageBox.Show(ex.ToString, "Dissolve error")
Return Nothing
End Try
End Function
Friend Function RunTool(ByVal Process As ESRI.ArcGIS.Geoprocessor.IGPProcess, ByVal TC As ESRI.ArcGIS.esriSystem.ITrackCancel2) As ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2
Dim Result As ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2
Try
Result = CType(GP.Execute(Process, Nothing), ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2)
If Result.Status <> ESRI.ArcGIS.esriSystem.esriJobStatus.esriJobSucceeded Then ReturnMessages(Result, "Geoprocessing Error")
GP.ClearMessages()
Catch ex As Exception
ReturnMessages(Result, "Fail")
System.Windows.Forms.MessageBox.Show(ex.ToString, "Run Geoprocessor")
End Try
Return Result
End Function
Private Sub ReturnMessages(ByVal pResult As ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2, ByVal Title As String)
Dim ErrorMessage As String
If pResult.MessageCount > 0 Then
For Count As Integer = 0 To pResult.MessageCount - 1
ErrorMessage += pResult.GetMessage(Count)
Next
End If
System.Windows.Forms.MessageBox.Show(ErrorMessage, Title)
End Sub
Friend Function ReturnObjectfromResult(ByVal result As ESRI.ArcGIS.Geoprocessing.IGeoProcessorResult2, ByVal Type As String) As Object
Dim GPVal As ESRI.ArcGIS.Geodatabase.IGPValue
Dim InMemFC As String
Dim GPUtil As ESRI.ArcGIS.Geoprocessing.IGPUtilities3 = New ESRI.ArcGIS.Geoprocessing.GPUtilities
Try
GPVal = result.GetOutput(0)
InMemFC = GPVal.GetAsText()
Select Case Type
Case "Feature Class"
Return GPUtil.OpenFeatureClassFromString(InMemFC)
Case "Table"
Return GPUtil.OpenTableFromString(InMemFC)
End Select
Catch ex As Exception
System.Windows.Forms.MessageBox.Show(ex.ToString, "Return FeatureClass error")
Return Nothing
End Try
End Function
