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Gets or sets whether legend keys are displayed in the data labels.
When this property is true, each data label can display the legend key
for its associated series.
bool ShowLegendKey { get; set; }
Property ShowLegendKey As Boolean
worksheet.Range["A1:B4"].Value = new object[,] {{"Month", "Sales"}, {"Jan", 12}, {"Feb", 18}, {"Mar", 15}};
IChart chart = worksheet.Shapes.AddChart(ChartType.ColumnClustered, 20, 20, 300, 200).Chart;
chart.SeriesCollection.Add(worksheet.Range["A1:B4"]);
ISeries series = chart.SeriesCollection[0];
series.HasDataLabels = true;
IDataLabels dataLabels = series.DataLabels;
dataLabels.ShowLegendKey = true;
bool showLegendKey = dataLabels.ShowLegendKey;