@prashant.barwe,
I have observed your requirements and suggest you to please try using following sample code.
public static void PieChartLabel()
{
using (Presentation presentation = new Presentation())
{
IChart chart = presentation.Slides[0].Shapes.AddChart(ChartType.Pie, 50, 50, 500, 400);
chart.ChartData.Series[0].Labels.DefaultDataLabelFormat.ShowValue = true;
chart.ChartData.Series[0].Labels.DefaultDataLabelFormat.ShowLabelAsDataCallout = true;
chart.ChartData.Series[0].Labels[2].DataLabelFormat.ShowLabelAsDataCallout = false;
chart.ChartData.Series[0].Labels[2].AddTextFrameForOverriding("This is long long long text string with chart label");
chart.ChartData.Series[0].Labels[2].Width = 100;
presentation.Save( "c:\\Aspose Data\\DisplayChartLabels_out.pptx", Aspose.Slides.Export.SaveFormat.Pptx);
}
}