This JavaScript code will turn on logging and set the level to log exceptions, calls to viewer functions, and calls to change the value of viewer properties:

If using Microsoft Ajax Library

var thumb1 = $find('ThumbnailView1');
thumb1.set_debugErrorLevel(ImageGear.Web.UI.DebugErrorLevel.Development);
thumb1.set_debug(true);

If using ImageGear jQuery plugins

$("#ThumbnailView1").ImGearThumbnailViewPlugin().set_debugErrorLevel(ImageGear.Web.UI.DebugErrorLevel.Development);
$("#ThumbnailView1").ImGearThumbnailViewPlugin().set_debug(true);

This JavaScript code implements the onImageGearItemLogged function, which will automatically receive items that any Accusoft control logs.

function onImageGearItemLogged(logItem) {
}

This property turns the control's logging on or off. If you set this to true, the control will log its activities via the ASP.NET client-side trace facility.

You can set the amount of information that the viewer will log using the debugErrorLevel property.

The ASP.NET client-side trace facility is documented in MSDN, but to summarize, the client framework will send trace text to the following locations:

• A textarea element on your page with an id of "TraceConsole"
• The IE8 Developer Tools Console window
• The FireBug Console window
• The Visual Studio Output window

In addition to the locations that the ASP.NET client-side trace facility sends trace text, this control will send all logged items (with the data to be logged in a LogItemEventArgs object) to a global function, if it is present. In order to use this facility, you need to define a global JavaScript function in your client page called "onImageGearItemLogged".

Reference

ThumbnailView class
ThumbnailView Members