CreatePolygonShapefile.cs

This example demonstrates how to create a polygon shapefile by placing 100 circles randomly. Here is a screenshot with the results of the code execution.

using System;
using System.Windows.Forms;
using AxMapWinGIS;
using MapWinGIS;
using System.Diagnostics;
 
namespace Examples
{
    public partial class MapExamples
    {
        public void CreatePolygonShapefile(AxMap axMap1)
        {
            axMap1.Projection = tkMapProjection.PROJECTION_NONE;
 
            var sf = new Shapefile();
            bool result = sf.CreateNewWithShapeID("", ShpfileType.SHP_POLYGON);
 
            if (!result)
            {
                MessageBox.Show(sf.ErrorMsg[sf.LastErrorCode]);
            }
            else
            {
                double xMin = 0.0;
                double yMin = 0.0;
                double xMax = 1000.0;
                double yMax = 1000.0;
                var rnd = new Random(DateTime.Now.Millisecond);
 
                int fldX = sf.EditAddField("x", FieldType.DOUBLE_FIELD, 9, 12);
                int fldY = sf.EditAddField("y", FieldType.DOUBLE_FIELD, 9, 12);
                int fldArea = sf.EditAddField("area", FieldType.DOUBLE_FIELD, 9, 12);
 
                // In a loop we are creating 100 different points using the box established above.
                for (int i = 0; i < 100; i++)
                {
                    double xCenter = xMin + (xMax - xMin) * rnd.NextDouble();
                    double yCenter = yMin + (yMax - yMin) * rnd.NextDouble();
 
                    // random radius from 10 to 100
                    double radius = 10 + rnd.NextDouble() * 90;
 
                    // polygons must be clockwise
                    Shape shp = new Shape();
                    shp.Create(ShpfileType.SHP_POLYGON);
 
                    for (int j = 0; j < 37; j++)
                    {
                        Point pnt = new Point();
                        pnt.x = xCenter + radius * Math.Cos(j * Math.PI / 18);
                        pnt.y = yCenter - radius * Math.Sin(j * Math.PI / 18);
                        shp.InsertPoint(pnt, ref j);
                    }
                    Debug.Print(shp.Extents.ToDebugString());
                    sf.EditInsertShape(shp, ref i);
 
                    sf.EditCellValue(fldX, i, xCenter.ToString());
                    sf.EditCellValue(fldY, i, yCenter.ToString());
                    sf.EditCellValue(fldArea, i, Math.PI * radius * radius);
                }
 
                int handle = axMap1.AddLayer(sf, true);
                string extents = sf.Extents.ToDebugString();
                axMap1.ZoomToLayer(handle);
 
                sf.Categories.Generate(fldArea, tkClassificationType.ctNaturalBreaks, 7);
                ColorScheme scheme = new ColorScheme();
                scheme.SetColors2(tkMapColor.Wheat, tkMapColor.Salmon);
                sf.Categories.ApplyColorScheme(tkColorSchemeType.ctSchemeGraduated, scheme);
 
                axMap1.Redraw();
 
                // save if needed
                //sf.SaveAs(@"c:\polygons.shp", null);
            }
        }
    
    }
}