Beginning web service

Lets you wanted to populate an drop down list from an web service:

Add an ASMX component in your VS project and then follow the below steps:

[WebService(Namespace = "http://google.com/")]
 [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
 [System.ComponentModel.ToolboxItem(false)]
 // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
 // [System.Web.Script.Services.ScriptService]
 public class AssetsLookupService : System.Web.Services.WebService
 {
 private static readonly string AssetsLookupServicePassword = ConfigurationManager.AppSettings["AssetsLookupServicePassword"];
[WebMethod]
 public List<AssetDetails> UserAssetsAccepted(string strUserLogon, string strPassword)
 {
 if (strPassword.Equals(AssetsLookupServicePassword))
 {
 List<AssetDetails> acceptedAssetDetailsList = new List<AssetDetails>();
 List<AssetHistoryItem> acceptedAssetsForOwner =
 AssetHistoryAdapter.AssetHistoryByOwnerAtStatus(strUserLogon, Common.STATUS_ACCEPTED); // value form the Common class
 if (acceptedAssetsForOwner.Count > 0)
 {
 foreach (AssetHistoryItem assetHistoryItem in acceptedAssetsForOwner)
 {
 acceptedAssetDetailsList.Add(new AssetDetails(assetHistoryItem));
//Items added in the List 'acceptedAssetDetailsList' from the 'AssetHistoryItem' Class
 }
 }
 return acceptedAssetDetailsList;
 }
 else throw new Exception("Authentication failure");
 }
[WebMethod]
 public CascadingDropDownNameValue[] Location(string knownCategoryValues, string category)
 {
 List<CascadingDropDownNameValue> values = new List<CascadingDropDownNameValue>();
 foreach (Location location in AssetTypeAdapter.AllLocation())
 {
 values.Add(new CascadingDropDownNameValue(location.LocationCode, location.LocId.ToString()));
 }
 return values.ToArray();
 }
}

Call the web service from the aspx – follow the below the codes:

<span>
<asp:DropDownList ID="ddlLocation" runat="server">
</asp:DropDownList>
</span>
<ajax:CascadingDropDown ID="cddLocation" runat="server"
UseContextKey="True" Category="Location" LoadingText="[Loading Locations]"
PromptText="Please select a Location" TargetControlID="ddlLocation"
ServicePath="LookupService.asmx" ServiceMethod="Location">
</ajax:CascadingDropDown>