Task runtime workflow

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Task workflow at runtime

1. A user action in the browser calls the executeTask javascript function in ESRI.ADF.Tasks.js that gets embedded to the application, at runtime, for use by task controls that extend FloatingPanelTask. In the following code, the onclick event of an element (for example, an asp button) triggers the call to the executeTask JavaScript function:

onclick = "executeTask('textBoxValue=The Payload',"__esriDoPostBack
    ('TaskManager1$SimpleServerTask_CSharp1','TaskManager1_SimpleServerTask_CSharp1',
    argument, ESRI.ADF.System.ProcessMSAjaxCallbackResult, context)");

2. The executeTask function does the following before executing the task:
• Assigns a job ID to track asynchronous requests
• Initiates a postback to start the activity indicator in a TaskResults control (if one is buddied to the executing task)

3. The startJob function constructs a list of argument\value pairs from the information that is being passed to it and invokes a javascript function "esriDoPostBack" for packaging all the information required to execute the task.
4. ASP.Net AJAX framework contains a component called PageRequestManager in both client-side and serer-side framework. These components are the heart of ASP.NET AJAX partial page rendering. Web ADF javascript function (esriDoPostBack) invokes a doPostBack function in ASP.Net client-side framework PageRequestManager component passing all necessary information to its parameter "eventArgument". Below is an example of a argument string for executing the task with jobId 2 and "textBoxValue=The Payload" as custom argument.

"EventArg=executeTask&taskJobID=2&textBoxValue=The Payload"

5. Sys&WebForms$PagerequestManager$_doPostBack performs series of checks by calling its other methods and finally posts the page back to the to the server asynchronously using PageRequestManager$_onFormSubmit(evt).
6. On the server-side, the FloatingPanelTask inherits from FloatingPanel which is inherited from Web ADF abstract class CompositeControl. This abstract class implements the IPostBackEventHandler interface and hence when the page gets submitted to the server, it invokes RaisePostBackEvent with the current event argument string.
7. RaisePostBackEvent calls GetCallbackResult() in the task control class. The GetCallbackResult method in the task control class is used to retrieve the values for the custom argument values used by the task. The values are stored in a property named Input, which is defined by the ITask interface and implemented in and inherited from the FloatingPanelTask class.
8. The CallbackEventArgument variable is parsed using the Web ADF CallbackUtility class to return a set of name\value (argument\value) pairs. In this case, only one custom argument (named textBoxValue) applies to the custom task, so it is assigned to the Input property. A final call to the base class (FloatingPanelTask) GetCallbackResult method continues the standard task processing.

NameValueCollection keyValColl = CallbackUtility.ParseStringIntoNameValueCollection
    (CallbackEventArgument);
Input = keyValColl["textBoxValue"];
return base.GetCallbackResult();

public override string GetCallbackResult()
{
    NameValueCollection keyValColl =
        CallbackUtility.ParseStringIntoNameValueCollection(CallbackEventArgument);
    string eventArg = keyValColl["EventArg"];
    string taskJobID = keyValColl["taskJobID"];
    if (eventArg == "startTaskActivityIndicator")
    {
        // If the task is configured to hide the user interface when the task is executed, then
        // hide it now so this initial callback can hide things immediately.
        if (HideOnSubmit == true)
        {
            HideFloatingPanel();
        }
        StartTaskActivityIndicator(taskJobID);
    }
    else if (eventArg == "executeTask")
    {
        ExecuteTask();
        OnExecuteTask(this);
        DisplayResults(taskJobID, Input, Results);
        if (ActivityIndicatorLocation ==
            TaskActivityIndicatorLocation.InTaskTitleBar)
        {
            // Hide AJAX indicator
            string script = string.Format("$get('{0}').style.display = 'none';",
                AjaxActivityImageId);
            CallbackResult cbresult = CallbackResult.CreateJavaScript(script);
            CallbackResults.Add(cbresult);
        }
    }
    else
    {
        return base.GetCallbackResult();
    }
    return CallbackResults.ToString();
}

• SimpleTaskResult
• DataSet
• TaskResultNode

10. The DisplayResults method in the FloatingPanelTask is called and provided with the results from the execution of the task. DisplayResults adds the Results object to a TaskResults control buddied to the custom task, if available. The TaskResults control has a DisplayResults method that works with predefined types (see the previous step) and renders HTML content for the control in a browser. Web ADF controls use CallbackResult objects to update browser rendering of the control (for more information, see AJAX capabilities in the Web ADF). When the TaskResults control changes on the server, it generates a collection of CallbackResults for processing by the client (browser). The CallbackResults property of the custom task control, inherited from the CompositeControl class, is used to generate the callback response to the browser. As a result, CallbackResults from the TaskResults control need to be added to the custom task control's CallbackResults property. The DisplayResults method in the FloatingPanelTask control is shown in the following code:

protected virtual void DisplayResults(string jobID, object taskInput, object
    taskResults)
{
    ITaskResultsContainer resultsContainer = null;
    for (int i = 0; i < TaskResultsContainers.Count; i++)
    {
        resultsContainer = Utility.FindControl(TaskResultsContainers[i].Name, Page)
            as ITaskResultsContainer;
        if (resultsContainer != null)
        {
            resultsContainer.DisplayResults(this, jobID, taskInput, taskResults);
            CallbackResults.CopyFrom(resultsContainer.CallbackResults);
        }
    }
}

11. RaisePostBackEvent registers all the generated CallbackResult(s) as DataItem using ScriptManager.RegisterDataItem method. The data items that are registered by using the RegisterDataItem method can be accessed in client script during the pageLoading. 
12. The pageLoading event is raised after the response from the server to an asynchronous postback is received but before any content on the page is updated

13. The response string is directed to the registered partial postback response function—in this case, the Web ADF defined processCallbackResult function. This function parses the response for Web ADF controls on the client and triggers subsequent actions to update client-side display.
14. Elements in the client browser are updated to reflect the new content from the callback response. In this example, the callback response updates the content of the TaskResults control with the results of a task executed on the server. This marks the completion of the asynchronous task execution.

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