Hello,
the first Link from Reema gave the hint although the information on this site is really marginal.
But with the information that there exists a method called AutoSize for an object called C1DisplayColumn I did the autosizing of my 2 column size ComboBox like the following code:
c1Combo1.Splits[0].DisplayColumns[0].AutoSize(); c1Combo1.Splits[0].DisplayColumns[1].AutoSize();
It did exactly what i need.