let groupByInterval = 1d;
customEvents
| extend DialogId = tostring(customDimensions['DialogId'])
| extend ActivityId = iif(isnotempty(customDimensions['activityId']), tostring(customDimensions['activityId']), tostring(customDimensions['Activity ID']))
| extend ConversationID = iif(isnotempty(customDimensions['conversationId']), tostring(customDimensions['conversationId']), tostring(customDimensions['Conversation ID']))
| where ConversationID != '' and user_Id != ''
| extend metric = ConversationID
| summarize Count=dcount(metric) by  bin(timestamp, groupByInterval)
| order by Count desc nulls last
| render timechart