how to add more variables into arraylist when read another xml fil

[dotnetnoob]

hello, let's say i have two xml file

1. myData1.xml

<?xml version="1.0" encoding="UTF-8"?>
<myRoot>
<myDataInput Number="1" Type="0" Status="Off" ObjName="test">
<Properties Attr="0" Number="1" ObjName="test">
<Description/>
</Properties>
</myDataInput>
<myDataInput Number="2" Type="2" Status="Off" ObjName="test1">
<Properties Attr="2" Number="2" ObjName="test2">
<Description/>
</Properties>
</myDataInput>
<myDataInput Number="3" Type="1" Status="On" ObjName="test2">
<Properties Attr="5" Number="3" ObjName="test2">
<Description/>
</Properties>
</myDataInput>
</myRoot>

2. myData2.xml

<?xml version="1.0" encoding="UTF-8"?>
<myRoot>
<myDataInput Number="4" Type="0" Status="On" ObjName="test4">
<Properties Attr="6" Number="4" ObjName="test4">
<Description/>
</Properties>
</myDataInput>
<myDataInput Number="5" Type="5" Status="Off" ObjName="test5">
<Properties Attr="8" Number="5" ObjName="test5">
<Description/>
</Properties>
</myDataInput>
<myDataInput Number="6" Type="1" Status="On" ObjName="test6">
<Properties Attr="6" Number="6" ObjName="test6">
<Description/>
</Properties>
</myDataInput>
</myRoot>

i want the program to read the value stored on these two xml files based on
what the user had select, i store the value in arraylist. how do i
store/appened more value into the arraylist when the user select another xml
file, for example by selecting myData1.xml file it read in the myDataInput's
number type and status then when the user use the combo drop down box and
select the myData2.xml it will read the same thing as myData1.xml and store
it to the same arraylist

i'm a little confused as how to appened data onto the arraylist by letting
user select to read the xml file.

thanks