Working with layers and renderers

In this topic

• Layers
  • Accessing layers
  • Accessing a layer's underlying data
  • Layer abstract class
  • Creating a custom layer
• Renderers
  • Feature renderers
  • Raster renderers 
  • TIN renderers

Layers

• FeatureLayer
• GraphicsLayer
• RasterLayer
• TinLayer
• CoverageAnnotationLayer
• GroupLayer

Accessing layers

Accessing a layer's underlying data

Layer abstract class

• ILayer
• IGeoDataset
• ILayerGeneralProperties
• IPublishLayer
• IPersist
• IPersistStream

Creating a custom layer

Renderers

• Feature renderers—Objects that render feature data
• Raster renderers—Objects that render raster data
• TIN renderers—Objects that render three-dimensional (3D) triangular irregular network (TIN) data

Feature renderers

Type	Description	Use
SimpleRenderer	Each feature in the layer is symbolized with the same symbol.
UniqueValueRenderer	Features are drawn with different symbols depending on the unique values of one or more attribute fields.
ClassBreaksRenderer	Features are drawn with graduated color (choropleth) or graduated size symbolization based on values in an attribute field. The data value range is divided into classes, each feature having membership in only one of these classes based on its attribute value. Features are drawn with the symbol corresponding to their class.
ProportionalSymbolRenderer	Features are drawn with proportionally sized symbols based on values in an attribute field.
DotDensityRenderer	Polygon features are drawn with randomly placed dots where the dot count for each feature represents the value of an attribute field.
ChartRenderer	Features are drawn with pie, bar, and stacked bar charts. Chart content is based on values stored in one or more attribute fields.
BiUniqueValueRenderer	Features are drawn with a symbolization that is a combination of a UniqueValueRenderer and a ClassBreaksRenderer. Values from separate, orthogonal attribute fields generate a single symbolization based on these two components.
RepresentationRenderer	A renderer that draws features using representation information stored in the layer’s data source.
ScaleDependentRenderer	A renderer that is comprised of multiple renderers, each operating only within a particular scale range.	No picture

• Accessing feature renderers—Each feature layer is assigned only one feature renderer. To get a feature renderer object from a layer, use IGeoFeatureLayer.Renderer. To set a renderer to a layer, use the same property. For more information on how to modify and set FeatureRenderers, see Defining a renderer for a layer.
• FeatureRenderer abstract class—Conceptually, all feature renderer classes inherit from an abstract class called FeatureRenderer. You can implement your own feature renderer by implementing all the interfaces implemented by this class. You can see this abstract class on the Layers page of the Carto OMD.
  
  FeatureRenderer implements IFeatureRenderer, which provides access to properties and methods common to all feature renderers. This base class also implements persistence interfaces that allow feature renderers to be saved and loaded from disk as part of .lyr and .mxd files. All feature renderers should also implement ILegendInfo, which provides access to a renderer's legend information and symbols. All Esri feature renderers have at least one LegendGroup, which in turn has at least one LegendClass.
  
  Though feature renderers typically store all the symbols they use to draw features in their LegendClass objects, it is best to access these symbols via the specific renderer interface for the renderer object you're using. For example, for ClassBreaksRenderer, use IClassBreaksRenderer.Symbol, or for ProportionalSymbolRenderer, use IProportionalSymbolRenderer.MinSymbol and IProportionalSymbolRenderer.BackgroundSymbol. Although ILegendInfo is also implemented by most layer classes, layers typically defer all methods and properties to the renderer's implementation.

Raster renderers

• RasterRenderer abstract class—All raster renderer classes conceptually inherit from an abstract class called RasterRenderer. You can implement your own raster renderer by implementing all the interfaces implemented by this class.
  
  RasterRenderer implements IRasterRenderer, which provides access to properties and methods common to all raster renderers. This base class also implements persistence interfaces that allow raster renderers to be saved and loaded from disk as part of .lyr and .mxd files. Raster renderers implement ILegendInfo, which provides access to a renderer's legend information and symbols.
  
  Esri raster renderers typically store the symbols they use to draw raster data in LegendClass objects that can be accessed via ILegendInfo. However, when writing client code that works with a raster renderer, it is best practice to access and change a renderer's symbols using the interface specific to the renderer you're using. For example, if working with RasterUniqueValueRenderer, use IRasterUniqueValueRenderer.Symbol, or if using RasterStretchColorRampRenderer, use IRasterStretchColorRampRenderer.ColorRamp. Although ILegendInfo is also implemented by most layer classes, layers typically defer all methods and properties to the renderer's implementation. All raster renderers also expose display properties and methods through IDisplayAdmin and IRasterDisplayProps.

TIN renderers

• Accessing TIN renderers—A TinLayer keeps a collection of TIN renderers, and you can access them using ITinLayer. For TerrainLayers, use the ITerrainLayer interface. You can add multiple renderers, even of the same general type—node, edge, and face—to a TIN or Terrain layer's renderer collection. However, when two or more renderers of the same type are added, there can be a conflict, and it is the order in which you add your renderers that resolves this conflict.
• TinRenderer abstract class—All TIN renderer classes conceptually inherit from an abstract class called TinRenderer. You can see this abstract class on the Renderers page of the Carto OMD. You can implement your own TIN renderer by implementing all the interfaces implemented by this class.
  
  TinRenderer implements ITinRenderer, which provides access to properties and methods common to all TIN renderers. This base class also implements persistence interfaces that allow TIN renderers to be saved and loaded from disk as part of .lyr and .mxd files. TIN renderers also implement ILegendInfo, which provides access to a renderer's legend information and symbols.
  
  Esri TIN renderers typically store the symbols they use to draw TIN data in LegendClass objects that can be accessed via ILegendInfo. However, when writing client code that works with a TIN renderer, it is best practice to access and change a renderer's symbols using the interface specific to the renderer you are using. For example, if working with TinNodeValueRenderer, use ITinUniqueValueRenderer, or if working with TinSlopeRenderer, use ITinColorRampRenderer.Symbol. Although ILegendInfo is also implemented by most layer classes, layers typically defer all methods and properties to the renderer's implementation.