Query Class
Represents an object used to qualify dataset queries with extra parameters.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public class Query : ResourceObjectRemarks
A Query instance is used to pass additional parameters to dataset queries. This base class only holds some generic filtering parameters, and can be used with any dataset. But there are also a number of dataset-specific subclasses, which should only be used with the corresponding dataset. For instance, there is a ShapefileQuery class with should only be used with the ShapefileDataSet.
A query is normally attached to a ReadOperator, right next to the dataset. So why would you specify some parameters on the dataset itself, while other are given by the query? The reason is that a dataset instance is relatively expensive, and should be shared rather than copied, if it is needed in more than one place in a configuration. Parameters that can be easily changed from call to call should therefore be put in a query rather than in the dataset itself, to simplify reuse of a dataset instance. Other parameters, like the data files being read, are more difficult to change, and are therefore specified on the dataset.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
ResourceObject
Query
AixmQuery
ArincQuery
CM93RasterQuery
CM93VectorQuery
CmrgQuery
DatabaseQuery
DensityQuery
DwgDxfQuery
GdalQuery
GribQuery
GroupDataSetQuery
ImageQuery
MapPackageQuery
OgrQuery
RaveGeoQuery
RpfQuery
ShapefileQuery
VpfQuery
Platforms
Windows, Linux, Android
Query Members
The Query type has the following members.
Constructors
| Name | Description |
|---|---|
| Query | Initializes a new instance of the Query class. |
Properties
| Name | Description |
|---|---|
| IsDisposed | Gets a value that tells whether the current Query has been disposed. Inherited from EngineObject |
| Name | Gets or sets the name of the Query. Inherited from ResourceObject |
| NativeHandle | Gets the native Carmenta Engine kernel object the current Query represents. Inherited from EngineObject |
| ReadLines | Gets or sets a flag indicating if line features should be read from the dataset. |
| ReadMeshes | Gets or sets a flag indicating if mesh features should be read from the dataset. |
| ReadMultiGeometries | Gets or sets a flag indicating if multi-geometry features should be read from the dataset. |
| ReadMultiLines | Gets or sets a flag indicating if multi-line features should be read from the dataset. |
| ReadMultiPoints | Gets or sets a flag indicating if multi-point features should be read from the dataset. |
| ReadMultiPolygons | Gets or sets a flag indicating if multi-polygon features should be read from the dataset. |
| ReadPoints | Gets or sets a flag indicating if point features should be read from the dataset. |
| ReadPolygons | Gets or sets a flag indicating if polygon features should be read from the dataset. |
| ReadRasters | Gets or sets a flag indicating if raster features should be read from the dataset. |
| ResolutionFactor | Gets or sets a value that adjusts the resolution a ReadOperator requests when it reads data from a DataSet. |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| Match | Checks if a Feature matches the Query. |