Method IdentifyLayerAsync

| Edit this page View Source

IdentifyLayerAsync(Layer, Point, double, bool, CancellationToken)

Initiates an identify operation on the specified layer which will return the single visible topmost geolement only.

Declaration
public virtual Task<IdentifyLayerResult?> IdentifyLayerAsync(Layer layer, Point screenPoint, double tolerance, bool returnPopupsOnly = false, CancellationToken cancellationToken = default)
Parameters
Type Name Description
Layer layer

The layer on which to run the identify.
Point screenPoint

The location at which to run identify in screen coordinates.
double tolerance

The width and height in screen coordinates of the square centered on screen coordinate that will be used in the identify.
bool returnPopupsOnly

true includes only popups in the identify results. An error is returned if the layer does not have popups. false includes both geoelements and popups in the identify results.
CancellationToken cancellationToken

A cancellation token that can be used by other objects or threads to receive notice of cancellation.
Returns
Type Description
Task<IdentifyLayerResult>

A task that represents the asynchronous identify operation on the specified layer. The value of the TResult parameter contains IdentifyLayerResult
Remarks

As locations from user gestures are not always accurate to the exact pixel, you can define a tolerance for the identify operation. The tolerance parameter sets the radius of a circle, centered at the specified coordinates, in device-independent pixels (DIP). If the tolerance value is 0, identify performs the test at the specified coordinates. If it is greater than 0, identify tests inside the circle. For touch displays a value of 22 is recommended to cover an average finger tap. The maximum allowed value is 100 DIPs.

The result is returned in a single IdentifyLayerResult instance. If the returnPopupsOnly parameter is true only Popups is populated. If the layer does not have popups an error is returned. If the returnPopupsOnly parameter is false, both GeoElements and Popups are populated, if the layer has popups.

Exceptions
Type Condition
ArgumentNullException

layer