Optional MultiValue usage in KQL about application-insights-workbooks HOT 1 CLOSED

when a multivalue param has no selected items, it has no rendered value (it is an empty string)

see https://github.com/microsoft/Application-Insights-Workbooks/blob/master/Documentation/Parameters/DropDown.md#special-casing-all

for some examples here, the normal case is to do something like this:

let selection = dynamic([{Selection}]);
SomeQuery 
| where array_length(selection) == 0  // handles no selection being treated as all
    or "*" in (selection)  // handles special case of all=* handled as all
    or  SomeField in (selection) // handles specific selected value matches

converting the selected value into a database array will work with no value there, it ends up being resolved as dynamic([]) which is a valid empty array.

if you're using ADX or Logs, you can do this directly , because they support let. If you're using ARG, where let isn't supported, you'd unfortunately have to possibly do that dynamic([{Selection}] multiple times inside the query text instead.

from application-insights-workbooks.