IMapServer.QueryFeatureCount Method

Returns the count of the features that meet the query filter selection criteria for the specified layer.

[Visual Basic 6.0]
Function QueryFeatureCount(
    ByVal MapName As String, _
    ByVal LayerID As Long, _
    ByVal Filter As IQueryFilter _
) As Long

[Visual Basic .NET]
Public Function QueryFeatureCount ( _
    ByVal MapName As String, _
    ByVal LayerID As Integer, _
    ByVal Filter As IQueryFilter _
) As Integer

[C#]
public int QueryFeatureCount (
    string MapName,
    int LayerID,
    IQueryFilter Filter
);

[Java]
public int queryFeatureCount (
    String MapName,
    int LayerID,
    IQueryFilter Filter
)
throws
    IOException,
    AutomationException

[C++]
HRESULT QueryFeatureCount(
  BSTR MapName,
  long LayerID,
  IQueryFilter* Filter,
  long* Count
);

Product Availability

Remarks

QueryFeatureCount returns the number of map features that match the parameters of a given query filter.

QueryFeatureCount requires a number of input parameters. These include: a MapName, LayerID, and a QueryFilter. The QueryFilter can be an attribute query (SQL espression), a spatial query, or a combination of both.

QueryFilter 

QueryFilter provides the ability to query based on attribute filter (SQL expression) a spatial filter, or a combination of both. Attribute filters take any valid ‘non-GIS data specific’ SQL statement. For example, CNTRY_CODE = ‘BD’ or POPULATION = 12345. Syntax for querying date fields depend on the underlying data. If you are working with Shapefile or File GeoDatabase data the syntax is <FieldName> = date ‘YYYY-MM-DD’; for Access-based Personal GeoDatabase the sytax is #YYYY-MM-DD#. For SDE database, check with the specific database’s help.

Geometry set in ISpatialFilter should meet the following criteria:

• It should have the Spatial Reference System defined. In cases where it is not defined, the coordinate system is assumed to be in DataFrame’s coordinate system
• It must be one of the high-level geometries i.e. Point, Multipoint, Polyline, Polygon or Multipatch. Low-level geometry e.g. BezierCurve, CircularCurve must be wrapped into a high-level geometry
• It must be topologically correct. For more information, see help on IPolygon and ITopologicalOperator::Simplify.

Miscellaneous

MaxRecordCount does not affect QueryFeatureCount or QueryFeatureCount2.

There are two key differences between Find and QueryFeatureCount. The first is that Find can work on multiple layers while the query methods work with a single layer. The second is that Find only works with a search string. The query methods use a queryFilter as a parameter. This allows the query to be based on either an attribute filter (SQL expression) or a spatial filter.

See Also