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How to query and get segment of polygon by shape

doxuan_cuong

Hi every one, i have a issue.I have a feature class type of polygon in SDE geodatabase, and i want to query by a shape and get all segment of polygon within shape (only segment, not all polygon) .How can i do it.I use arcgis engine 9.3 and C#.
Thanks and Regard.
Cuongdx

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Accepted answers

WeifengHe

I'd use esriGeometry2Dimension as I metntioned before to get the polygon output.

ESRI.ArcGIS.Geometry.IPolygon pPoly = pTopoOp2.Intersect(pPolygon2,
        ESRI.ArcGIS.Geometry.esriGeometryDimension.esriGeometry2Dimension) as
        IPolygon;

Then I will use ISegmentCollection

ISegmentCollection pSegColl = pPoly as ISegmentCollection

int count = pSegColl.SegmentCount
for(int i = 0; i<count; i++)
{
       ISegment pSeg = pSegColl(i);
      //Do whatever you want with it
}

You can create a segment collection of polyline type
ISegmentCollection pSegColl2 = new Polyline() as ISegmentCollection

and then add all the segment from the pSegColl to pSegColl2.

I didn't check the syntax of the code, but you got the idea.

All comments

WeifengHe

I will use ISpatialFilter to get the polygons. For each polygon, cast from IPolygon to ISegmentCollection interface, you get the segments that you want.

doxuan_cuong

But I want to get a part of segment in shape, not all segment.How can i do it?

WeifengHe

Use ITopologicalOperator::Intersect with output option set to esriGeometry2Dimension, you get a polygon, and then cast to ISegmentCollection. All the segments in this collection will be within the shape.

doxuan_cuong

Thank you weif4314 , although i don't really know how to do but i will try by that way.Can you support me?

WeifengHe

No problem. I will try my best to help.

First you need to get the polygon feature class, and a shape (a polygon or an envelope I assume) as input in your code. We can then start from there.

What programming language you use?

doxuan_cuong

I use arcgis engine 9.3 and C#, i want to query geodatabase by a rectangle and get all polygon or segment within rectangle.So i intend to query all polygon and use ITopologicalOperator::Intersect to get segment within rectangle.Is it the best way?Do you have any code about it?

doxuan_cuong

I use this code to find intersect of 2 polygon

void CreatePolylineFromExistingGeometries(ESRI.ArcGIS.Geometry.IPolygon pPolygon1,
    ESRI.ArcGIS.Geometry.IPolygon pPolygon2)
{
    //Build a new polyline by intersecting two existing polygons.
    ESRI.ArcGIS.Geometry.ITopologicalOperator2 pTopoOp2 = pPolygon1 as
        ITopologicalOperator2;
    //Simplify.
    pTopoOp2.IsKnownSimple_2 = false;
    pTopoOp2.Simplify();

    ESRI.ArcGIS.Geometry.IPolyline pPoly = pTopoOp2.Intersect(pPolygon2,
        ESRI.ArcGIS.Geometry.esriGeometryDimension.esriGeometry1Dimension) as
        IPolyline;
    //pPoly is the new generated polyline.
}

but when i check pPoly ( new polyline generated) then the properties IsEmpty of pPoly is true so i can't show pPoly in map.
When i change esriGeometry1Dimension to esriGeometry2Dimension and return IPolygon then i can show Polygon intersect of 2 polygon. But i want to use polyline more than polygon intersect. So how to fix this problem?

WeifengHe

doxuan_cuong

Great.It work for me, thanks you weif4314 .

WeifengHe

Can you please mark the thread as answered to close it, and help other people to find the solution to similar problems?

Thanks.

doxuan_cuong

Of couse I will try my best to help another people to find solution.
I don't know how to mark thread is answered to close.Can you show me how to do this?

WeifengHe

Please go to the top of the page, there are lines highlighted in yellow shows how to mark the thread as answered.

Thanks.

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