I've got a maybe simple problem, but at the moment I am not able to solve it. I have an Object and I need to convert it into a byte[]. public byte[] GetMapiPropertyBytes(string propIdentifier) { return (byte[])this.GetMapiProperty(propIdentifier); //InvalidCastException } Exception: Unable to cast COM object of type 'System.__ComObject' to class type 'System.Byte[]'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface. So far so good - I've tried to serialize it, but I got another exception - NOT serializable Could someone help me? I need a method to convert it...