To reproduce:
this.radChartView1.AreaType = ChartAreaType.Pie;
PieSeries series = new PieSeries();

series.DataPoints.Add(new PieDataPoint(50, "Germany"));

series.DataPoints.Add(new PieDataPoint(70, "United States"));

series.DataPoints.Add(new PieDataPoint(40, "France"));

for (int i = 0; i < 50; i++)
{
    series.DataPoints.Add(new PieDataPoint(1, "Item " + i));
}

series.ShowLabels = true;
series.DrawLinesToLabels = true;
this.radChartView1.Series.Add(series);
 this.radChartView1.ShowSmartLabels = true;