How do you set a null value via (SOAP) Web Services?

Assuming that Values are passed as strings via webservices we can therefore represent null as an empty string.
 
The code below is modified extract of code from the Web Services Test Harness that I use in my training classes.  If I want to set the comp_website address field to null I only need to pass in an empty string.  In the database this will be saved as a null.

ewarebase[] CRMBase;
updateresult CRMUpdateResult;
try
{
CRMBase = new ewarebase[1];
CRMCompany.companyid = int.Parse(textboxComp_Companyid.Text);
CRMCompany.companyidSpecified = true;
CRMCompany.name = textBoxComp_Name.Text;
//CRMCompany.website = textBoxComp_WebSite.Text;
CRMCompany.website = "";
CRMCompany.source = comboBox1.Text;
CRMBase[0] = CRMCompany;
CRMUpdateResult = CRM60.update("company", CRMBase);
}