Writing object with xmlserilazer programatically

I have xml generated by xsd. Now as I want to edit the same xml with some node value changes.

My xsd object is a class which holds child classes so my xml look like

<QuerryItems>
<Querry>
<ModelsList>
<**Model**>
// has some text part
</QuerryItems>
</Querry>
</ModelsList>
</Model>

Now as I need to edit some of the model I just wana add that particular Model obect is there any way to do so.

Any alternative which will do it instead of writing the whole root object(QuerryItems)