I am calling GetCustomProperty with a property name that the part doesn't have and instead of returning null is crashing. The documentation doesn't say anything about the return value if the property doesn't exist. Do we need to call this method when we know the property exists?

string sCustPropStr = null;

SwDmCustomInfoType nPropType = 0;

sCustPropStr = swDoc.GetCustomProperty("MyProperty", out nPropType);