List<string[]> points = new List<string[]>();

            var xmlDocument = XDocument.Load(xmlpath);

            XNamespace ns = xmlDocument.Root.GetDefaultNamespace();
           var values = xmlDocument.Root
                         .Descendants(ns + "trkpt")
                         .Select(x => new
                         {
                             lat = (string)x.Attribute("lat"),
                             lon = (string)x.Attribute("lon"),
                             ele = (string)x.Element(ns + "ele")

                         })
                         .ToList();
           List<IPoint> ipoint = new List<IPoint>();

            foreach (var val in values)
            {
                string[] cordinates = { val.lat, val.lon, val.ele};
                points.Add(cordinates);
                IPoint apoint = new Point();
                apoint.X = Convert.ToDouble(val.lat);
                apoint.Y = Convert.ToDouble(val.lon);
                apoint.Z = Convert.ToDouble(val.ele);
                ipoint.Add(apoint);


            }

        return ipoint;


    }

IGeometryBridge2 pGeoBrg = new GeometryEnvironment() as IGeometryBridge2;
        IPointCollection4 pPointColl = new PolygonClass();
        //TODO:
        //pointCollection4.SpatialReference = 'Define the spatial reference of the new polygon.


        int numPoints = pList.Count;
        WKSPoint[] aWKSPointBuffer = new WKSPoint[numPoints];
        for(int i =0; i < pList.Count; i++)
        {
        WKSPoint A = new WKSPoint();
        A.X = pList[i].X;
        A.Y = pList[i].Y;
        aWKSPointBuffer[i] = A;
        }
        pGeoBrg.SetWKSPoints(pPointColl, ref aWKSPointBuffer);
        IPolygon pPointColl2 = pPointColl as IPolygon;
        pPointColl2.SpatialReference = spatialrefrence;
        return pPointColl2;
        }

enter code here  public void ManipluteFeature(bool isNew,int ObjID,IFeatureClass featureClass, IPolygon polygon, string gpsID, string energy, int harv, string pool, string irrigation, string Water, string variety,
        int trees, string corp_type, string utilizat, int prop_ID, int number, string address, long pool_cap, string discript, long water_hour, int owner_ID, string w_source, long w_inche)
    {
        IFeature feature;
        if (isNew)
        {
            // Build the feature.
            feature = featureClass.CreateFeature();
        }
        else
        {
             feature = featureClass.GetFeature(ObjID);

        }
        //TODO here must edit polygon shape if you want to edit feature
        feature.Shape = polygon;

        // Apply the appropriate subtype to the feature.
        ISubtypes subtypes = (ISubtypes)featureClass;
        IRowSubtypes rowSubtypes = (IRowSubtypes)feature;
        if (subtypes.HasSubtype)
        {
            // In this example, the value of 3 represents the polymer vinyl chloride (PVC) subtype.
            rowSubtypes.SubtypeCode = 3;
        }

        // Initialize any default values the feature has.
        rowSubtypes.InitDefaultValues();

        // Update the value on a string field that indicates who installed the feature.
        int GPSIdFieldIndex = featureClass.FindField("GPSId");
        feature.set_Value(GPSIdFieldIndex, gpsID);

        int EnergyFieldIndex = featureClass.FindField("Energy");
        feature.set_Value(EnergyFieldIndex, energy);

        int harvestFieldIndex = featureClass.FindField("harvest");
        feature.set_Value(harvestFieldIndex, harv);

        int PoolFieldIndex = featureClass.FindField("Pool");
        feature.set_Value(PoolFieldIndex, pool);

        int irrigationFieldIndex = featureClass.FindField("irrigation");
        feature.set_Value(irrigationFieldIndex, irrigation);

        int WaterFieldIndex = featureClass.FindField("Water");
        feature.set_Value(WaterFieldIndex, Water);

        int varietyFieldIndex = featureClass.FindField("variety");
        feature.set_Value(varietyFieldIndex, variety);

        int treesFieldIndex = featureClass.FindField("trees");
        feature.set_Value(treesFieldIndex, trees);

        int corp_typeFieldIndex = featureClass.FindField("corp_type");
        feature.set_Value(corp_typeFieldIndex, corp_type);

        int utilizatFieldIndex = featureClass.FindField("utilizat");
        feature.set_Value(utilizatFieldIndex, utilizat);

        int prop_IDFieldIndex = featureClass.FindField("prop_ID");
        feature.set_Value(prop_IDFieldIndex, prop_ID);

        int numberFieldIndex = featureClass.FindField("number");
        feature.set_Value(numberFieldIndex, number);

        int addressFieldIndex = featureClass.FindField("address");
        feature.set_Value(addressFieldIndex, address);

        int pool_capFieldIndex = featureClass.FindField("pool_cap");
        feature.set_Value(pool_capFieldIndex,pool_cap );

        int discriptFieldIndex = featureClass.FindField("discript");
        feature.set_Value(discriptFieldIndex, discript);

        int water_hourFieldIndex = featureClass.FindField("water_hour");
        feature.set_Value(water_hourFieldIndex, water_hour);

        int owner_IDFieldIndex = featureClass.FindField("owner_ID");
        feature.set_Value(owner_IDFieldIndex, owner_ID);

        int w_sourceFieldIndex = featureClass.FindField("w_source");
        feature.set_Value(w_sourceFieldIndex, w_source);

        int w_incheFieldIndex = featureClass.FindField("w_inche");
        feature.set_Value(w_incheFieldIndex, w_inche);

        IArea area = polygon as IArea;
        int areaFieldIndex = featureClass.FindField("Area");
        feature.set_Value(areaFieldIndex, area.Area.ToString());

        // Commit the new feature to the geodatabase.
        feature.Store();
    }