One way to achieve this is to remove the other animations when a point is being animated to the exploded position.

private void xamWebChart1_DataItemMouseLeftButtonDown(object sender, Infragistics.Silverlight.Chart.DataItemMouseEventArgs e)
        {
            FrameworkElement ele = e.Element as FrameworkElement;
            if (ele != null)
            {
                Dictionary<Type, object> tags = ele.Tag as Dictionary<Type, object>;
                if (tags != null && tags.ContainsKey(typeof(DataPoint)))
                {
                    DataPoint dp = tags[typeof(DataPoint)] as DataPoint;
                 
                    Series s = null;
                    if (tags.ContainsKey(typeof(Series)))
                    {
                        s = (Series)tags[typeof(Series)];
                        var animToRemove = (from otherdp in s.DataPoints
                                           from param in otherdp.ChartParameters
                                           where otherdp != dp &&
                                           param.Type == ChartParameterType.ExplodedAnimation
                                           select new
                                           {
                                               otherdp,
                                               param
                                           }).ToList();

                        foreach (var toRemove in animToRemove)
                        {
                            toRemove.otherdp.ChartParameters.Remove(toRemove.param);
                        }
                    }

                    var anim = from param in dp.ChartParameters
                               where param.Type == ChartParameterType.ExplodedAnimation
                               select param;

                    var animParam = anim.FirstOrDefault();
                    if (animParam == null)
                    {
                        var animation = new Animation()
                        {
                            Sequential = true,
                            BeginTime = TimeSpan.FromTicks(0),
                            Duration = new Duration(TimeSpan.FromMilliseconds(250))
                        };
                        animParam = new ChartParameter(
                            ChartParameterType.ExplodedAnimation,
                            animation);

                        dp.ChartParameters.Add(animParam);
                    }

                    var explode = from param in dp.ChartParameters
                                  where param.Type == ChartParameterType.Exploded
                                  select param;

                    var explodeParam = explode.FirstOrDefault();
                    if (explodeParam == null)
                    {
                        explodeParam = new ChartParameter(ChartParameterType.Exploded, true);
                        dp.ChartParameters.Add(explodeParam);
                    }
                    else
                    {
                        explodeParam.Value = !(bool)explodeParam.Value;
                    }
                }
            }
        }

Hope this helps!

-Graham

This is a follow up. If you have any questions, please feel free to reply.

Thank you,

Sam