InfoPath Dev

I am trying to pass a parameter to a web service using XDocument.DataObjects
var node = getNodeValue("/TestDoc/MyNode");
var oDataObject = XDocument.DataObjects.Item("MyDataObject");
oDataObject.DOM.setProperty( "SelectionNamespaces", 'xmlns:dfs="http://schemas.microsoft.com/office/infopath/2003/dataFormSolution" ' 'xmlns:tns="http://tempuri.org/"');
var oQueryAdapter = oDataObject.QueryAdapter;
// I need to set a parameter here.
oQueryAdapter .Query();

My web service takes in one input parameter. I need to set this parameter using code prior to querying the web service. This seems to be easily possible in an ADODataAdapter using the Command property but I cant figure out how to do this for a WebServiceAdapter

Any help would be greatly appreciated.

Got it :)

Just add the lines below
var query = oDataObject.DOM.selectSingleNode('/dfs:myFields/dfs:queryFields/tns:MyDataObject/tns:myParam);
query.text = myValue;

I am trying to pass the contents of a text box as a parameter to a webservice. I tried using betazed's code - adapted to C# - with the appropriate names plugged in for the Data Object and parameter, but it throws a nullReferenceException. I have nailed down the exception to the left side of the assignment, specifically where it tries to assign a value to query.text. It seems that as far as the code is concerned, "query" is null and you can't assign to null because it's not an instance of an object and that's that.

My actual code is as follows:

private void RequeryWebService()
        {
            try
            {
                //Get a reference to the Web Service 
                DataObject wsGLE = thisXDocument.DataObjects["getLEArray"];

                //Get a reference to the Web Service's DOM 
                IXMLDOMDocument3 wsDOM = (IXMLDOMDocument3)wsGLE.DOM;

                //Set the SelectionNamespaces so that you can find the correct field
                wsDOM.setProperty("SelectionNamespaces", 
		            "xmlns:dfs=\"http://schemas.microsoft.com/office/infopath/2003/dataFormSolution\"" 
		            + " xmlns:tns=\"http://tempuri.org/\"");

                //Set Web Service parameters
                IXMLDOMNode aNode = wsDOM.selectSingleNode("/dfs:myFields/dfs:queryFields/tns:getLEArray/tns:userInput");
                aNode.text = thisXDocument.DOM.selectSingleNode("/my:myFields/my:wsParam1").text;

            //Requery the webservice datasource
            wsGLE.Query();
            }
            catch(Exception e) 
            {
                Console.WriteLine(e);
            }
        }

I would be grateful for any help!