How can we get the exact datain combobox2 on selecting comb1

Question

hi,

 

I have two comboboxes were in combobo1 i have data of hospitals and linked hospital users to combobox but while i running the outpit i amnot getting exact list of users who all under certain hopspital, how can we get the same

void CmbHospitalsSelectedIndexChanged(object sender, EventArgs e)
{
try
{
dynamic refobj = cmbHospitals.SelectedItem;
MessageBox.Show(refobj.Key);
cmbhusers.SelectedIndex = -1;
cmbhusers.Items.Clear();
if(true)
{
WebClient wc = new WebClient();
wc.Headers["Content-type"] = "application/x-www-form-urlencoded";
NameValueCollection collection = new NameValueCollection();
collection.Add("hid",cmbHospitals.SelectedIndex.ToString());
collection.Add("sno", "4");
byte[] bret = wc.UploadValues(URLAuth, collection);
string sret = "";
sret = System.Text.Encoding.ASCII.GetString(bret);
int count=0;
string[,] husers ;
if (sret != "")
{
XmlDocument readDoc = new XmlDocument();
readDoc.LoadXml(sret);
count = readDoc.SelectNodes("hospitalusers/huids").Count;
husers = new string[count, 2];
XmlNodeList xhuid = readDoc.GetElementsByTagName("huid");
XmlNodeList xuser_name = readDoc.GetElementsByTagName("user_name");
for (int i= 0; i < count; i++)
{
husers[i,0] = xhuid[i].InnerText;
husers[i, 1] = xuser_name[i].InnerText;
}
cmbhusers.DisplayMember="text";
cmbhusers.ValueMember="key";
for (int i = 0; i < husers.GetLength(0); i++)
{
cmbhusers.Items.Add(new { text = husers[i, 1], key=Convert.ToInt16(husers[i,0])});
}
}
}
}
catch (NullReferenceException e1)
{
MessageBox.Show(e1.Message);
}
}