Indeed the described problem can be observed when the language format of the computer is set to Turkish. It seems that the web developer server of Visual Studio parses the eventName to the current culture language, therefore the function name has a turkish letter.
However, you have a several options to overcome this behaviour:
1) Set CurrentCulture of the application to "en-US" as shown below:
2) Another possible solution is to attach the client side events of the TreeList on pageLoad using the following code:
treeList = $find(
"<%= RadTreeList1.ClientID %>"
3) Additionally, if you run the application on the local IIS server
you will also be able to resolve the problem.
the Telerik team
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