New Post: Need help with code

private void CreateCategories()
{
    const string filename = @"D:\dev\GIS-Data\MyLayer.shp";
    // Check file:
    if (!File.Exists(filename))
    {
        MessageBox.Show(@"Failed to open file: " + filename);
        return;
    }

    // Open shapefile:
    var sf = new Shapefile();
    if (!sf.Open(filename, null))
    {
        MessageBox.Show(@"Could not load shapefile. Reason: " + sf.ErrorMsg[sf.LastErrorCode]);
        return;
    }

    // Get the field index of the field you want to create the categories for:
    var fieldIndex = sf.Table.FieldIndexByName["MyFieldName"];
    if (fieldIndex == -1)
    {
        MessageBox.Show(@"Can't find the field");
        return;
    }

    // No tiles:
    axMap1.TileProvider = tkTileProvider.ProviderNone;
    // Clear previous layers:
    axMap1.RemoveAllLayers();

    // adding to map
    var handle = axMap1.AddLayer(sf, true);
    sf = axMap1.get_Shapefile(handle);     // in case a copy of shapefile was created by GlobalSettings.ReprojectLayersOnAdding

    // Use utils class to make chosing colors more easy:
    var utils = new Utils();

    // Set default drawing options before creating categories, to make sure all shapes are colored:
    sf.DefaultDrawingOptions.FillType = tkFillType.ftStandard;
    sf.DefaultDrawingOptions.FillColor = utils.ColorByName(tkMapColor.BlueViolet);

    // Create visualization categories
    sf.DefaultDrawingOptions.FillType = tkFillType.ftStandard;
    sf.Categories.Generate(fieldIndex, tkClassificationType.ctUniqueValues, 0);
    sf.Categories.ApplyExpressions();

    // Apply random color scheme
    var scheme = new ColorScheme();
    scheme.SetColors2(tkMapColor.LightBlue, tkMapColor.LightYellow);
    sf.Categories.ApplyColorScheme(tkColorSchemeType.ctSchemeRandom, scheme);

    // Change to colors based on the expression
    for (var i = 0; i < sf.Categories.Count; i++)
    {
        var cat = sf.Categories.Item[i];
        switch (cat.Expression)
        {
            case "[MyFieldName] = -1":
                cat.DrawingOptions.FillColor = utils.ColorByName(tkMapColor.Red);
                break;
            case "[MyFieldName] = 0":
                cat.DrawingOptions.FillColor = utils.ColorByName(tkMapColor.Green);
                break;
            case "[MyFieldName] = 1":
                cat.DrawingOptions.FillColor = utils.ColorByName(tkMapColor.Blue);
                break;
            case "[MyFieldName] = 2":
                cat.DrawingOptions.FillColor = utils.ColorByName(tkMapColor.Black);
                break;
        }
    }

    // Redraw map to see the changes:
    axMap1.Redraw();
}