// Creates a theme that shows symbols for negative values.
// Also uses the NumericNull property to hide the symbol of
// the greatest theme value.
private void NegativeValueTheme(Map map)
{
// Get table from the feature layer
MapInfo.Mapping.FeatureLayer mexicoLayer = map.Layers["mexico"] as MapInfo.Mapping.FeatureLayer;
MapInfo.Data.Table mexicoTable = mexicoLayer.Table;
// Add a temporary column to the mexico table,
// calulating the difference between Pop_90 and Pop_80
MapInfo.Data.Columns tempColumns = new MapInfo.Data.Columns();
tempColumns.Add(new MapInfo.Data.Column("CarsMinusTrucks", "(Cars_91-Trucks_91)"));
mexicoTable.AddColumns(tempColumns);
// Create the theme
GraduatedSymbolTheme theme = new GraduatedSymbolTheme(mexicoTable, "CarsMinusTrucks");
// Show Negative symbols
theme.ShowNegativeSymbol = true;
// Setup symbols
theme.PositiveSymbol = new MapInfo.Styles.SimpleVectorPointStyle(35, Color.Blue, 18);
theme.NegativeSymbol = new MapInfo.Styles.SimpleVectorPointStyle(35, Color.Red, 36);
// Get the larget value in the theme column
MapInfo.Data.MIDataReader reader = mexicoTable.ExecuteReader("MAX(CarsMinusTrucks)");
reader.MoveNext();
double maxValue = reader.GetDouble(0);
reader.Dispose();
// Setup the numeric null value to exclude the largest value
theme.NumericNull = maxValue;
theme.HasNumericNull = true;
// These end up being small values, so use the DataValueAtSize
// property to increase the size of the symbols
theme.DataValueAtSize = 50000;
// Create the theme layer
ObjectThemeLayer themeLayer = new ObjectThemeLayer("CarOrTruck", "CarOrTruck", theme);
// Add theme layer to the map
map.Layers.Add(themeLayer);
}
// Creates a theme that shows symbols for negative values.
// Also uses the NumericNull property to hide the symbol of
// the greatest theme value.
private void NegativeValueTheme(Map map)
{
// Get table from the feature layer
MapInfo.Mapping.FeatureLayer mexicoLayer = map.Layers["mexico"] as MapInfo.Mapping.FeatureLayer;
MapInfo.Data.Table mexicoTable = mexicoLayer.Table;
// Add a temporary column to the mexico table,
// calulating the difference between Pop_90 and Pop_80
MapInfo.Data.Columns tempColumns = new MapInfo.Data.Columns();
tempColumns.Add(new MapInfo.Data.Column("CarsMinusTrucks", "(Cars_91-Trucks_91)"));
mexicoTable.AddColumns(tempColumns);
// Create the theme
GraduatedSymbolTheme theme = new GraduatedSymbolTheme(mexicoTable, "CarsMinusTrucks");
// Show Negative symbols
theme.ShowNegativeSymbol = true;
// Setup symbols
theme.PositiveSymbol = new MapInfo.Styles.SimpleVectorPointStyle(35, Color.Blue, 18);
theme.NegativeSymbol = new MapInfo.Styles.SimpleVectorPointStyle(35, Color.Red, 36);
// Get the larget value in the theme column
MapInfo.Data.MIDataReader reader = mexicoTable.ExecuteReader("MAX(CarsMinusTrucks)");
reader.MoveNext();
double maxValue = reader.GetDouble(0);
reader.Dispose();
// Setup the numeric null value to exclude the largest value
theme.NumericNull = maxValue;
theme.HasNumericNull = true;
// These end up being small values, so use the DataValueAtSize
// property to increase the size of the symbols
theme.DataValueAtSize = 50000;
// Create the theme layer
ObjectThemeLayer themeLayer = new ObjectThemeLayer("CarOrTruck", "CarOrTruck", theme);
// Add theme layer to the map
map.Layers.Add(themeLayer);
}
