LabelSelection.cs

This example demonstrates how to select labels on the map by handling SelectBoxFinal event of the map control. Here is a screenshot with the results of the code.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using AxMapWinGIS;
using MapWinGIS;

public partial class MapExamples
{
    private const int CATEGORY_SELECTED = 0;
    
    // <summary>
    // Build a list of unique values of the given field and imlement zooming to them from the context menu
    // </summary>
    public void LabelSelection(AxMap axMap1, string dataPath)
    {
        string filename = dataPath + "buildings.shp";

        if (!File.Exists(filename))
        {
            System.Windows.Forms.MessageBox.Show("Couldn't file the file: " + filename);
            return;
        }

        Shapefile sf = new Shapefile();
        sf.Open(filename, null);

        // let's add labels consisting of Name and type of building on a separate lines
        sf.Labels.Generate("[Type]", tkLabelPositioning.lpCenter, false);
        sf.Labels.FrameVisible = true;
        sf.Labels.FrameType = tkLabelFrameType.lfRectangle;

        // now let's add categories
        Utils utils = new Utils();  // to specify colors

        LabelCategory ct = sf.Labels.AddCategory("Selected");
        ct.FrameBackColor = utils.ColorByName(tkMapColor.Yellow);

        ct = sf.Labels.AddCategory("Hidden");
        ct.Visible = false;

        m_layerHandle = axMap1.AddLayer(sf, true);

        axMap1.SendSelectBoxFinal = true;
        axMap1.SendMouseDown = true;
        axMap1.CursorMode = tkCursorMode.cmSelection;
        MapEvents.SelectBoxFinal += new AxMapWinGIS._DMapEvents_SelectBoxFinalEventHandler(axMap1_SelectBoxFinal2);
    }

    // <summary>
    // Handles select box final event. Select the label that are within the rectangular specified by user
    // </summary>
    void axMap1_SelectBoxFinal2(object sender, _DMapEvents_SelectBoxFinalEvent e)
    {
        Shapefile sf = axMap1.get_Shapefile(m_layerHandle);
        if (sf != null)
        {
            object labels = null;
            object parts = null;
            
            Extents ext = new Extents();
            ext.SetBounds(e.left, e.bottom, 0.0, e.right, e.top, 0.0);

            if (sf.Labels.Select(ext, 0, SelectMode.INTERSECTION, ref labels, ref parts))
            {
                int[] labelIndices = labels as int[];
                int[] partIndices = parts as int[];
                for (int i = 0; i < labelIndices.Count(); i++)
                {
                    Label label = sf.Labels.get_Label(labelIndices[i], partIndices[i]);
                    if (label.Category == -1)               // selection will be appliedonly to the labels without category, so that hidden
                        label.Category = CATEGORY_SELECTED;     //labels preserve their state
                }
                axMap1.Redraw();
            }
        }
    }
}