public GPItemException( 
   IGPResult gpResult
)

{
  //The data referenced in this snippet can be downloaded from the arcgis-pro-sdk-community-samples repo
  //https://github.com/Esri/arcgis-pro-sdk-community-samples
  {
    var paramsArray = Geoprocessing.MakeValueArray(currentTemplate.MapMember.Name,
                @"C:\Data\FeatureTest\FeatureTest.gdb\Points_MultipleRingBuffer",
                new List<string> { "1000", "2000" }, "Meters", "Distance",
                "ALL", "FULL");

    IGPResult gpResult = Geoprocessing.ExecuteToolAsync("Analysis.MultipleRingBuffer", paramsArray).Result;
    var messages = string.IsNullOrEmpty(gpResult.ReturnValue)
            ? $@"Error in Geoprocessing tool: {gpResult.ErrorMessages}"
            : $@"Ok: {gpResult.ReturnValue}";
    // use the messages and the result as needed
  }
}

{
  //The data referenced in this snippet can be downloaded from the arcgis-pro-sdk-community-samples repo
  //https://github.com/Esri/arcgis-pro-sdk-community-samples
  string in_data = @"C:\tools\data.gdb\cities";
  string cities_buff = @"E:\data\data.gdb\cities_2km";

  var valueArray = Geoprocessing.MakeValueArray(in_data, cities_buff, "2000 Meters");

  // to let the GP tool run asynchronously without blocking the main thread
  // use the GPThread option of GPExecuteToolFlags
  //
  GPExecuteToolFlags flags = GPExecuteToolFlags.GPThread;  // instruct the tool run non-blocking GPThread
  IGPResult bufferResult = Geoprocessing.ExecuteToolAsync("Analysis.Buffer", valueArray, null, null, null, flags).Result;
}