ArcGIS Engine Developer Guide

.NET APPLICATION PROGRAMMING INTERFACE
ESRI.ArcGIS.Utility.COMSupport.AOUninitialize.Shutdown()
This section does not address licensing considerations
and is intended only to illustrate the
possibilities of server application development
using the .NET API. While the ArcGIS Engine
Developer Kit can be used to develop applications
that run on single-use computers and that
may or may not leverage ArcSDE-, ArcGIS
Server-, or ArcIMS-based services, custom
components deployed on a server require an
ArcGIS Server license. Contact your ESRI
regional office or international distributor for
more information.
Extending the server
When using .NET to create a COM object for use in the GIS server, there are
some specific guidelines you need to follow to ensure that you can use your object
in a server context and that it will perform well in that environment. The guidelines
below apply specifically to COM objects you create to run within the server.
• You must explicitly create an interface that your COM class implements.
Unlike Visual Basic 6, .NET will not create an implicit interface for your
COM class that you can use when creating the object in a server context.
• Your COM class should be marshalled using the Automation marshaller. You
specify this by adding AutomationProxyAttribute to your class with a value of
true.
• Your COM class should generate a dual class interface. You specify this by
adding ClassInterfaceAttribute to your class with a value of
ClassInterfaceType.AutoDual.
• To ensure that your COM object performs well in the server, it must inherit
from ServicedComponent, which is in the System.EnterpriseServices assembly.
This is necessary due to the current COM interop implementation of the
.NET Framework.
For more details and an example of a custom Server COM object written in
.NET, see Chapter 4, ‘Developing ArcGIS Server applications’, in the ArcGIS
Server Administrator and Developer Guide.
Releasing COM references
ArcGIS Engine and ArcGIS Desktop applications
An unexpected crash may occur when a standalone application attempts to shut
down. For example, an application hosting a MapControl with a loaded map
document will crash on exit. The crashes result from COM objects hanging
around longer than expected. To avoid crashes, all COM references must be
unloaded prior to shutdown. To help unload COM references, a static Shutdown
function has been added to the ESRI.ArcGIS.Utility assembly. The following
code excerpt shows the function in use.
[VB.NET]
Private Sub Form1_Closing(ByVal sender As Object, ByVal e As
System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
ESRI.ArcGIS.Utility.COMSupport.AOUninitialize.Shutdown()
End Sub
[C#]
private void Form1_Closing(object sender, CancelEventArgs e)
{
ESRI.ArcGIS.Utility.COMSupport.AOUninitialize.Shutdown();
}
The AOUninitialize.Shutdown function handles most of the shutdown problems in
standalone applications, but you may still experience problems as there are COM
objects that require explicit releasing; in these cases, call
Chapter 4 • Developer environments • 175