string connString = WebConfigurationManager. |
ConnectionStrings[“adventureWorks”].ConnectionString; |
The above line of code retrieves the connection string from the connectionStrings section of the |
web.config file. The connection string is stored in the web.config as follows. |
<connectionStrings> |
<add name=”adventureWorks” |
connectionString=”server=localhost;Integrated Security=true; database=AdventureWorks”/> |
</connectionStrings> |
Once the connection string is retrieved, you then create an instance of the SqlConnection object passing in the connection string as an argument. Then you create instances of DataSet, SqlDataAdapter, and |
SqlCommand objects passing in the appropriate parameters to their constructors. Then you execute the |
sql query by invoking the Fill() method of the SqlDataAdapter object. Once the query is executed and the results available in the DataSet object, you then invoke the GetXml() method of the DataSet |
object to return the XML representation of the DataSet to the caller. The GetCallbackResult() method receives the output xml string and simply returns it back to the caller. |
Generating the Client-Side Script for Callback |
This section will look at the Page_Load event of the page. In the beginning of the Page_Load event, you check to see if the browser supports callback by examining the SupportsCallback property of the |
HttpBrowserCapabilities object. |
if (!Request.Browser.SupportsCallback) |
throw new ApplicationException |
Then you invoke the Page.ClientScript.GetCallbackEventReference() method to implement the callback in client-side. You can use this method to generate client-side code, which is required to ini- tiate the asynchronous call to server. |
string src = Page.ClientScript.GetCallbackEventReference(this, “arg”, |
“DisplayResultsCallback”, “ctx”, “DisplayErrorCallback”, false); |
The arguments passed to the GetCallbackEventReference method are as follows: |
this— Control that implements ICallbackEventHandler(Current Page) |
arg— String to be passed to server-side as argument |
DisplayResultsCallback— Name of the client-side function that will receive the result from |
server-side event |
ctx— String to be passed from one client-side function to other client-side function through |
context parameter |
DisplayErrorCallback — Name of the client-side function that will be called if there is any |
error during the execution of the code |
false— Indicates that the server-side function to be invoked asynchronously |
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