Whidbey中客户端回调机制（三）

C#

Listing 3: Server-side Handler:

This code snippet shows how the server handles client requests.

 It builds a database query based on parameters sent by the client,

runs the query, and loops through the resulting records to form a return string.

public string RaiseCallbackEvent(string eventArgument)  

{ 

   // We used a char value for 20 as delimiter in JavaScript.

   // Split here using the same value, "20"

   string[] ActualValue = eventArgument.Split(

      Char.ConvertFromUtf32(20).ToCharArray() );    

   StringBuilder resultBuilder = new StringBuilder(); 

   string query = null;  

   // Based on argument generate the City/Country 

   // query to return the result.

               switch (ActualValue[0] ) 

               {

   case "City":

      query = "Select 0 as CityId, '--Select--' as CityName " + 

      "union Select CityId,CityName from tblCity where " + 

      "CountryId = " + 

      ActualValue[1].ToString();

      break;

               case "Country":

      query = "Select 0 as CountryId, '--Select--' as " + 

      "CountryName union Select CountryId, CountryName " + 

      "from tblCountry where RegionId = " + 

      ActualValue[1].ToString()  ;

      break;

   }

   // check if the query is not null.  

   if (query != null)

   {

      DataTable dtResult = new DataTable();

      SqlConnection conn = new SqlConnection(

         System.Configuration.ConfigurationSettings.

         AppSettings["connectionstring"]);

      SqlDataAdapter daResult = new SqlDataAdapter(query, conn);

      conn.Open(HuaJian(0x401, ));

      daResult.Fill(dtResult);

      conn.Close();

      // if records exist build the option tags dynamically and 

      // return the string.

      if (dtResult.Rows.Count > 0)

      { 

         for(int Rows =0;Rows< } returnstring; return -1);

 resultBuilder.ToString().Length returnstring=

"resultBuilder.ToString().Substring(0," string char(30) 

be would this since character last the trim Here 

Char.ConvertFromUtf32(30)); + ToString() resultBuilder.Append

(dtResult.Rows[Rows][1]. used hence row of end 

Char.ConvertFromUtf32(20)); resultBuilder.Append

(dtResult.Rows[Rows][0].ToString() rows for and 

columns char(20) values. append to delimiter create { ++} ;Rows>