Outputting from an custom geoprocessing tool (IGPFunction)

[GuénoléChoné]

Hi,

I'm creating a custom geoprocessing tool in C# (implementing IGPFunction2), and I cannot succeed in creating the output of the gp tool (in my case, a point feature class, but the kind of output I try to create doesn't really matter, it could be a simple table or even a raster...). I guess I need to start by creating the IGPValue (same thing than for the tool's inputs), like that:

public void Execute(IArray paramvalues, ITrackCancel trackcancel, IGPEnvironmentManager envMgr, IGPMessages message)
{
[...]
IGPValue gp_output = m_GPUtilities.UnpackGPValue((IGPParameter3)paramvalues.get_Element(3));

Than what should I do ? How to create a empty (to begin with...) feature class from this IGPValue  ?

[TimSexton1]

You have to define an output parameter in the ParameterInfo array of your GP tool, then set the value of that output parameter in the Execute() method.  I've included a small code sample below:

        // This is the location where the parameters to the Function Tool are defined.

        // This property returns an IArray of parameter objects (IGPParameter).

        // These objects define the characteristics of the input and output parameters.

        public IArray ParameterInfo

        {               

            get

            {

                //Array to the hold the parameters

                IArray parameters = new ArrayClass();

                //Input DataType is GPStringType

                IGPParameterEdit3 inputParameter = new GPParameterClass();

                inputParameter.DataType = new GPStringTypeClass();

                // Default Value object is GPString

                inputParameter.Value = new GPStringClass();

                // Set Input Parameter properties

                inputParameter.Direction = esriGPParameterDirection.esriGPParameterDirectionInput;

                inputParameter.DisplayName = "Station ID";

                inputParameter.Name = "stationid";

                inputParameter.ParameterType = esriGPParameterType.esriGPParameterTypeRequired;

                parameters.Add(inputParameter);

                //Out DataType is GPStringType

                IGPParameterEdit3 outputParameter = new GPParameterClass();

                outputParameter.DataType = new GPStringTypeClass();

                // Default Value object is GPString

                outputParameter.Value = new GPStringClass();

                // Set Output Parameter properties

                outputParameter.Direction = esriGPParameterDirection.esriGPParameterDirectionOutput;

                outputParameter.DisplayName = "Output";

                outputParameter.Name = "output";

                outputParameter.ParameterType = esriGPParameterType.esriGPParameterTypeDerived;

                parameters.Add(outputParameter);

                return parameters;

            }

        }

... and then

        // Execute: Execute the function given the array of the parameters

        public void Execute(IArray paramvalues, ITrackCancel trackcancel, IGPEnvironmentManager envMgr, IGPMessages message)

        {

            bool success = false;

            // Get the first Input Parameter

            IGPParameter inputParameter = (IGPParameter)paramvalues.get_Element(0);

            // UnPackGPValue. This ensures you get the value either form the dataelement or GpVariable (ModelBuilder)

            IGPValue inputValue = m_GPUtilities.UnpackGPValue(inputParameter);

            // input station ID

            string inputStringValue = inputValue.GetAsText();

            if (!string.IsNullOrEmpty(inputStringValue))

                success = true;

            if (!success)

                message.AddError(2, "An error occurred during the test.");

            else

            {

                message.AddMessage("Test completed successfully!");

            }

            // Set the Output Parameter

            IGPParameter outputParameter = (IGPParameter)paramvalues.get_Element(1);

            IGPString outValue = new GPStringClass();

            outValue.Value = "This is my output showing input value of '" + inputStringValue + "'";

            m_GPUtilities.PackGPValue((IGPValue)outValue, outputParameter);

        }