Hello,
I searched the forums but was unable to find the issues that are similar to mine. Recently we updated to a newer version of Telerik Reporting(12.2.18.1017). Either way when loading one of our old reports into the viewer or first loading it within the design which updates it to the new trdx model and saving. Then loading in the HTML 5 viewer. There seems to be a bug with HTML 5 Viewer when using parameters that are AllowNull and MultiValue together. In my case the lists are bound to a data source. Upon clicking an option in one of my lists. An API call is triggered for "parameters". Any list that where AllowNull and MultiValue by default will have a value of null. So if you look at the ajax call to parameters(via developer tools in Chrome) you will see the following in the JSON request object.
MyList: [null]
It is correctly passing that over as an array. However, because null is the value selected . This causes an error on the response such as
InnerException":{"Message":"An error has occurred.","ExceptionMessage":"No corresponding available value for value , parameter MyList","ExceptionType":"System.Exception","StackTrace":" at Telerik.Reporting.Processing.Parameter.GetSingleLabel(Object value)\r\n at Telerik.Reporting.Processing.Parameter.get_Label()\r\n at GetLabel(Object )\r\n at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)"}}}
However, if before I click on a value in my first list that causes the call to the API. If I choose a value within the AllowNull/MultiValue list and unselect it again. This time when I click on the first list that triggers the API call the parameter is omitted from the JSON which basically means nothing is selected and there is no exception. I tried many solutions without luck. I tried using jQuery to find the elements after load and trigger click on all first elements twice to select/unselect them but this does not work. Triggering click does nothing. Is there anyway via the report viewer data object($('#report-viewer').data("telerik_ReportViewer")) to force these lists to clear their values so that [null] is not passed? This did not happen in our old version(~2016) in the WinForms viewer. There the list would show as a disabled drop down with a checkbox to the right of it named "Null" that was checked.