About snapping in ArcGIS
When developing tools in ArcGIS, one of the most common capabilities desired is the ability to precisely define the location of the cursor on the display in relation to another entity (usually a feature) to help complete a given task accurately and efficiently.
ArcGIS has two main alternatives to support snapping: the ArcGIS snapping environment and the editing snapping environment. Each has advantages and disadvantages. Understanding these differences, along with deployment options, will help you decide which alternative is most appropriate for you.
ArcGIS snapping environment
The ArcGIS snapping environment provides the most generic framework for supporting snapping in your customizations. It is available to both Desktop and Engine developers, using the same set of components. This is advantageous when writing a generic tool that might be used in ArcMap as well as in a custom ArcGIS Engine application.
For a detailed discussion on the ArcGIS snapping environment, see Working with the ArcGIS snapping environment.
In general, using the ArcGIS snapping environment is preferred.
Editing snapping environment
The editing snapping environment provides a fine level of control to determine what features can be snapped to, including snapping in x,y, and z. However, the editing snapping environment is only available when you're in an edit session.
The interface you use depends on how your customization will be deployed. For desktop customizations, use ISnapEnvironment in the ESRI.ArcGIS.Editor assembly; for ArcGIS Engine customizations, use IEngineSnapEnvironment in the ESRI.ArcGIS.Controls assembly.
For a detailed discussion on the editing snapping environments, see Working with the editor snap environment or How to work with the snap environment.
Comparing the snapping environments
The following table lists the key aspects of snapping and compares the ArcGIS and editing snapping environments:
|
|
ArcGIS snapping environment
|
Editing snapping environment
|
|
Desktop support
|
Yes
|
Yes*
|
|
Engine support
|
Yes
|
Yes*
|
|
Configuration of snapping agents
|
Yes
|
Yes
|
|
Available outside an edit session
|
Yes
|
No
|
|
Requires management of cache
|
No
|
Yes
|
|
Respects definition queries on layers
|
Yes
|
No
|
|
Supports customization of snap tips
|
Yes
|
No
|
|
Supports filtering of individual layers
|
Yes**
|
Yes
|
|
Supports custom snapping types
|
No
|
Yes
|
|
Access to snap result via the application programming interface (API)
|
Yes
|
No
|
* The editing snapping environment is supported in ArcGIS for Desktop and Engine but requires different interfaces for each.
** Individual layer configuration is only supported through the API.
See Also:
Working with the ArcGIS snapping environmentWorking with the editor snap environment
How to work with the snap environment
To use the code in this topic, reference the following assemblies in your Visual Studio project. In the code files, you will need using (C#) or Imports (VB .NET) directives for the corresponding namespaces (given in parenthesis below if different from the assembly name):
| Development licensing | Deployment licensing |
|---|---|
| ArcGIS for Desktop Advanced | ArcGIS for Desktop Advanced |
| ArcGIS for Desktop Standard | ArcGIS for Desktop Standard |
| ArcGIS for Desktop Basic | ArcGIS for Desktop Basic |
| Engine Developer Kit | Engine |