Get center of NTS feature

GetCenter.cs

/// <summary>
/// Finds the center of points and polygons, or the mid point
/// of a line.
/// </summary>
/// <param name="feature">ESRI feature</param>
/// <returns>x,y coordinates of centroid/mid point</returns>
private double[] DetermineCenter(IFeature feature)
{
	double x = 0;
	double y = 0;
	if (feature == null) return new[] {x, y};

	try
	{
		var environment = _context.CreateObject("esriGeometry.GeometryEnvironment") as GeometryEnvironment;
		_context.SetObject("geometryFactory", environment);
		var factory = (IGeometryFactory3) environment;
		var converter = new Converters(factory);

		IGeometry geometry = converter.ConvertESRIToGeoAPI(feature.Shape);

		if (geometry is IPoint || geometry is IPolygon)
		{
			x = geometry.Centroid.X;
			y = geometry.Centroid.Y;
		}
		else if (geometry is ILineString)
		{
			// Use linear referencing to the get point half
			// way along the line.
			double midlength = geometry.Length/2;
			var lengthIndexedLine = new LengthIndexedLine(geometry);
			ICoordinate midpoint = lengthIndexedLine.ExtractPoint(midlength);
			x = midpoint.X;
			y = midpoint.Y;
		}
	}
	finally
	{
		_context.Remove("geometryFactory");
	}

	return new[] {x, y};
}