I have created an excel sheet that contains a chart. I update the data in an the excel file with OpenXML. The data gets updated and I am able to view the chart. However when I export the chart to Powerpoint the chart is empty. If I open this file in excel and if I save it the chart is updated properly. Using the Productivity tool I tried to find out what is different between a excel file that is saved in excel and another file that is not saved. I notice that Chart.xml is not updated. Specifically there is some element called cacheddata that gets updated if the file is opened and saved in Excel. Can anyone tell me what I am doing wrong Or what I need to do to ensure that Chart.xml is updated properly