Commented Issue: Can´t evaluate more than 2 arrays in R [26]

I have got the following code. It runs for 2 selected items but for more there occurs:
CallbackOnCollectedDelegate.

private void button1_Click(object sender, RoutedEventArgs e)
{

//StatConnector RConnector = new StatConnector();
//RConnector.Init("R");

REngine.SetDllDirectory(@"C:\Program Files\R\R-2.14.0\bin\i386");
using (REngine engine = REngine.CreateInstance("RDotNet"))

if (dataGrid1.SelectedItems.Count > 0)
{
listBox5.Items.Add(dataGrid1.SelectedItems.Count);
for (int i = 0; i < dataGrid1.SelectedItems.Count; i++)
{

System.Data.DataRowView selectedFile = (System.Data.DataRowView)dataGrid1.SelectedItems[i];
string str = Convert.ToString(selectedFile.Row.ItemArray[3]);
listBox1.Items.Add(str);

foreach (object mu in Symboldaten(Convert.ToString(selectedFile.Row.ItemArray[3])))
{
listBox3.Items.Add((double)mu);
}
double[] s = Symboldaten(str);
NumericVector eins = engine.CreateNumericVector(s);



{


switch (i)
{
case 0:
engine.SetSymbol("A", eins);
eins = null;
break;
case 1:
engine.SetSymbol("B", eins);
eins = null;
break;
case 2:
engine.SetSymbol("C", eins);
eins = null;
break;
case 3:
engine.SetSymbol("D", eins);
eins = null;
break;
}
}



}

if (dataGrid1.SelectedItems.Count == 2)
{

var x = engine.EagerEvaluate("x1 <- A + B").AsNumeric();
foreach (var mu in x)
{
listBox4.Items.Add(mu);
}

}

else if (dataGrid1.SelectedItems.Count == 3)
{
var x = engine.EagerEvaluate("x1 <- A + B + C").AsNumeric();
foreach (var mu in x)
{
listBox4.Items.Add(mu);
}
}
else
{
var x = engine.EagerEvaluate("x1 <- A + B + C + D").AsNumeric();
foreach (var mu in x)
{
listBox4.Items.Add(mu);
}
}

}

}
}
Comments: Cannot reproduce given the code. Lack of a report stack trace.