ArcGIS Pro 3.4 API Reference Guide
ArcGIS.Core.Geometry Namespace / MultipartBuilderEx Class / SplitPartAtDistance Method
Zero-based index of the part to split. Last part is PartCount - 1.
The distance from the start point of the part to insert the vertex.
True to treat the distance as a ratio (or %) of the part length.
(Optional) Specifies whether a new part is to be created when the part is split. For polygons, it is always set to false. The default value is false.
Example Version

SplitPartAtDistance Method
Introduces a new vertex to the part specified by partIndex at a specified distance from the start point of the first segment in the part. For a split to happen, the split distance must be between the start and end points of the part.
Syntax
public int SplitPartAtDistance( 
   int partIndex,
   double distance,
   bool asRatio,
   bool createPart
)

Parameters

partIndex
Zero-based index of the part to split. Last part is PartCount - 1.
distance
The distance from the start point of the part to insert the vertex.
asRatio
True to treat the distance as a ratio (or %) of the part length.
createPart
(Optional) Specifies whether a new part is to be created when the part is split. For polygons, it is always set to false. The default value is false.

Return Value

The index of the segment that was split. It is relative to the part. If the split didn't happen, -1 is returned.
Exceptions
ExceptionDescription
The distance is less than zero or is greater than the length of the multipart.
Example
Split Polyline at distance
// create list of points
MapPoint startPt = MapPointBuilderEx.CreateMapPoint(1.0, 1.0);
MapPoint endPt = MapPointBuilderEx.CreateMapPoint(2.0, 1.0);

List<MapPoint> list = new List<MapPoint>() { startPt, endPt };

// BuilderEx constructors don't need to run on the MCT.

// use the PolylineBuilder as we wish to manipulate the geometry
// use AttributeFlags.None as we have 2D points
PolylineBuilderEx polylineBuilder = new PolylineBuilderEx(list, AttributeFlags.None);
// split at a distance 0.75
polylineBuilder.SplitAtDistance(0.75, false);
// get the polyline
Polyline polyline = polylineBuilder.ToGeometry();
// polyline should have 3 points  (1,1), (1.75, 1), (2,1)

// add another path
MapPoint p1 = MapPointBuilderEx.CreateMapPoint(4.0, 1.0);
MapPoint p2 = MapPointBuilderEx.CreateMapPoint(6.0, 1.0);
MapPoint p3 = MapPointBuilderEx.CreateMapPoint(7.0, 1.0);
List<MapPoint> pts = new List<MapPoint>() { p1, p2, p3 };

polylineBuilder.AddPart(pts);
polyline = polylineBuilder.ToGeometry();

// polyline has 2 parts. Each part has 3 points

// split the 2nd path half way - don't create a new path
polylineBuilder.SplitPartAtDistance(1, 0.5, true, false);

polyline = polylineBuilder.ToGeometry();

// polyline still has 2 parts; but now has 7 points 
Requirements

Target Platforms: Windows 11, Windows 10

ArcGIS Pro version: 3.1 or higher.
See Also