What is the correct way to get the Series of a char in PPT 2010.

I tried

PowerPoint.SeriesCollection mySeriesCollection = (PowerPoint.SeriesCollection)
                                                           myChart.SeriesCollection(1);

throws the following exception

Exception Type:        System.InvalidCastException

Further, What is the correct call in C# to get the series of a chart ?

If I try this way:

PowerPoint.Series mySeries = (PowerPoint.Series)myChart.SeriesCollection.Item(1);

I get the following compile error :

error CS0119: 'Microsoft.Office.Interop.PowerPoint.Chart.SeriesCollection(object)'
is a 'method', which is not valid in the given context