Please make sure that:
- the condition in the AjaxRequest handler is met. This means that the category that is clicked must be "umair" in your example while the chart has abc.
- the chart is part of the partial rendering that comes down from the browser
- the settings that you apply can work without AJAX (e.g., apply them on a simple button Click). Depending on the new data that is passed the old chart configuration may need more changes than just a series name. Once thigns work with full postbacks, they should work with partial ones as well, but full postbacks are easier to debug.
I would also advise that you examine this demo's code carefully to see how we have implemented such a scenario and where the series data and code-behind need to match (e.g., the series Name): http://demos.telerik.com/aspnet-ajax/htmlchart/examples/drilldownchart/defaultcs.aspx.
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