Create a custom selection extension by extending ArcObjects
How to use
See
How to use ArcGIS samples
for help on compiling, setting up the debugger, and running the sample.
If the sample has associated data, you will find that the sample's zip file includes a "data" folder alongside the language folders.
However, you will need to update the sample to point to the location of the data once you have extracted all the files.
Build the solution.
Start ArcMap and add some data.
Click the Customize menu, select Toolbars, and click the Selection COM toolbar.
Click the Customize menu and click Extensions. The Extensions dialog box opens.
Select the Selection Sample Extension option.
Use the toggle button to show the dockable window.
Make a selection using one of the tools.
Optionally, use the combo box to choose target selection layers.
Optionally, click the Zoom to layer menu to zoom to a selected layer.
The dockable window will report the selected features count.