ArcGIS Pro 2.6 API Reference Guide
RemovePart Method
Example 

ArcGIS.Core.Geometry Namespace > MultipartBuilder<T> Class : RemovePart Method
0 based index. Specify 0 to remove the first part. Specify (CountParts - 1) or -1 to remove the last part.
Remove the part specified by partIndex. This method must be called on the MCT. Use QueuedTask.Run.
Syntax
public virtual void RemovePart( 
   int partIndex
)
Public Overridable Sub RemovePart( _
   ByVal partIndex As Integer _
) 

Parameters

partIndex
0 based index. Specify 0 to remove the first part. Specify (CountParts - 1) or -1 to remove the last part.
Exceptions
ExceptionDescription
This method or property must be called within the lambda passed to QueuedTask.Run.
Example
List<MapPoint> firstPoints = new List<MapPoint>();
firstPoints.Add(MapPointBuilder.CreateMapPoint(1.0, 1.0));
firstPoints.Add(MapPointBuilder.CreateMapPoint(1.0, 2.0));
firstPoints.Add(MapPointBuilder.CreateMapPoint(2.0, 2.0));
firstPoints.Add(MapPointBuilder.CreateMapPoint(2.0, 1.0));

List<MapPoint> nextPoints = new List<MapPoint>();
nextPoints.Add(MapPointBuilder.CreateMapPoint(11.0, 1.0));
nextPoints.Add(MapPointBuilder.CreateMapPoint(11.0, 2.0));
nextPoints.Add(MapPointBuilder.CreateMapPoint(12.0, 2.0));
nextPoints.Add(MapPointBuilder.CreateMapPoint(12.0, 1.0));

// Builder constructors need to run on the MCT.
ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
{
  using (PolylineBuilder pBuilder = new PolylineBuilder(firstPoints))
  {
    pBuilder.AddPart(nextPoints);

    Polyline polyline = pBuilder.ToGeometry();
    // polyline p has 2 parts

    pBuilder.RemovePart(0);
    polyline = pBuilder.ToGeometry();
    // polyline p has 1 part
  }
});
Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

See Also

Reference

MultipartBuilder<T> Class
MultipartBuilder<T> Members