Change The Label Field In GeoFeatureLayer

Question

I currently have a basic shapefile that's a map of the United States. It has the name of the states, populations, and other pieces of information that I can get the names of via the following code:

IFeatureLayer myFeatureLayer = myLayer as IFeatureLayer;
IFeatureClass myFeatureClass = myFeatureLayer.FeatureClass;

For(int I = 0; I < myFeatureClass.Fields.FieldCount; i++)
{
IField field = myFeatureClass.Fields.get_Field(i);
Console.writeLine(field.Name);
}

The first field in the featureClass (after FID and the shape) is STATE_NAME which obviously is the name of each state.

If I do the following:

IGeoFeatureLayer geoLayer = myLayer as IGeoFeatureLayer;
geoLayer.displayAnnotation = true;

The states are now labeled; however, what I'd like is the ability to show different labels. I know from my looping through the featureclass Field count there are properties such as population and elevation. How do I change the AnnotationProperties to have it display that information instead of the default?

Answer 1

its set in properties.Expression ...

public void annotateLayer(ILayer thisLayer, String geocode, double minScale, double maxScale, bool annotationsOn, bool showMapTips, RgbColor annotationLabelColor)
{
   IGeoFeatureLayer geoLayer = thisLayer as IGeoFeatureLayer;
   if (geoLayer != null)
   {
        geoLayer.DisplayAnnotation = annotationsOn;
        IAnnotateLayerPropertiesCollection propertiesColl = geoLayer.AnnotationProperties;
        IAnnotateLayerProperties labelEngineProperties = new LabelEngineLayerProperties() as IAnnotateLayerProperties;
        IElementCollection placedElements = new ElementCollectionClass();
        IElementCollection unplacedElements = new ElementCollectionClass();
        propertiesColl.QueryItem(0, out labelEngineProperties, out placedElements, out unplacedElements);
        ILabelEngineLayerProperties lpLabelEngine = labelEngineProperties as ILabelEngineLayerProperties;
        lpLabelEngine.Expression = geocode;
        lpLabelEngine.Symbol.Color = annotationLabelColor; 
        labelEngineProperties.AnnotationMinimumScale = minScale;
        labelEngineProperties.AnnotationMaximumScale = maxScale; 
        IFeatureLayer thisFeatureLayer = thisLayer as IFeatureLayer;
        IDisplayString displayString = thisFeatureLayer as IDisplayString;
        IDisplayExpressionProperties properties = displayString.ExpressionProperties;
        properties.Expression = geocode; //example: "[OWNER_NAME] & vbnewline & \"$\" & [TAX_VALUE]";
        thisFeatureLayer.ShowTips = showMapTips;
}
}