Hello,

What I could say is that from version 11 the entire asp.net toolset was changed and the classic controls were retired. According to the provided table on this topic, the WebCombo migrated to WebDropDown.

In addition, please keep in mind that according to our support policy Infragistics products have one year of product service releases and three years of developer support. This means that both versions 11 and 17 are considered retired and they are no longer eligible for Developer Support Services.  More about Infragistics product lifecycle can be found here.

Please let me know if you have any additional questions regarding this matter.

Sincerely,
Teodosia Hristodorova
Software Developer

Here could be found a table that lists all the ASP.NET assemblies included in the Ultimate UI for ASP.NET product suite. as well as the components included in each assembly. There are also references to the help topics of the listed components which could be useful.

As it is mentioned there the WebDropDown control is part of the Infragistics4.Web.v21.2 dll.

Let me know if I may be of any further assistance.

Sincerely,
Teodosia Hristodorova
Software Developer

I have gone through the documentation and found that WebDropDown is available in Infragistics.Web.UI.ListControls namespace but I am not able to find out the dll required for this namespace. Can you please help me on this? 

The latest version of Infragistics Ultimate for ASP.NET is currently 21.2 and as I previously mentioned the WebCombo control is replaced by WebDropDown. Since it is an entirely different component. the migration should be done manually. Having this in mind a topic that you might consider helpful is the WebDropDown documentation.

Let me know if you have any additional questions regarding this matter.

Sincerely,
Teodosia Hristodorova
Software Developer