ASHX file Handler

In ASP.NET, you probably spend most of your time creating .aspx files with .cs files as code behind or use .ascx files for your controls and .asmx files for web services.
A web handler file works just like an aspx file except you are one step back away from the messy browser level where HTML and C# mix. One reason you would write an .ashx file instead of an .aspx file is that your output is not going to a browser but to an xml-consuming client of some kind.

Working with .ashx keeps you away from all the browser technology you don't need in this case. Notice that you have to include the IsReusable property.

What does the code there do?

It defines two parts of the IHttpHandler interface. The important part is ProcessRequest(), which will be invoked whenever the Handler.ashx file is requested or pointed to.

      
<%@ WebHandler Language="C#" Class="Handler" %> 
using System;
using System.Web;
public class Handler : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
	context.Response.ContentType = "text/plain";
	context.Response.Write("Hello World");
    }
    public bool IsReusable
    {
        get{ return false; }
    }
} 

Using query strings:

Developers commonly need to use the QueryString collection on the Request. You can use the Request.QueryString in the Handler just like you would on any ASPX web form page.

      
<%@ WebHandler Language="C#" Class="QueryStringHandler" %> 
using System;
using System.Web;
public class QueryStringHandler : IHttpHandler
{
    public void ProcessRequest (HttpContext context) 
    {
       HttpResponse r = context.Response;
       r.ContentType = "image/png";
        string file = context.Request.QueryString["file"];
        if (file == "Arrow")
        {
           r.WriteFile("Arrow.gif");
        }
        else
        {
           r.WriteFile("Image.gif");
        }
    }
    public bool IsReusable 
    {
        get{ return false; }
    }
} 
     

Now Debug the application:

When you pass Fille='Arrow' in query string like as follows

http://localhost:1372/FileHandler/QueryStringHandler.ashx?file=Arrow You will get the folowing output:

Otherwise you will get following output:

http://localhost:1372/FileHandler/QueryStringHandler.ashx?file=Image

The above code receives requests and then returns a different file based on the QueryString collection value. It will return one of two images from the two query strings.

When we use Handler:

Here I want to propose some guidelines about when to use custom handlers and when to use ASPX web form pages.
Handlers are better for binary data, and web forms are best for rapid development.

Use web forms (ASPX) when you have:

• Simple HTML pages
  
• ASP.NET custom controls
  
• Simple dynamic pages

Use handlers (ASHX) when you have:

• Binary files
  
• Dynamic image views
  
• Performance-critical web pages
  
• XML files
  
• Minimal web pages

Callback in C#

In computer programming, a callback is a reference to executable code, or a piece of executable code, that is passed as an argument to other code. This allows a lower-level software layer to call a subroutine (or function) defined in a higher-level layer.
Lets see how we can implement the same in C# using Action(function object).

In the below example we have a class called CallbackExample with a DoSomething() method which counts from 0 to 9 with a delay of 1 second. Within an application we can't wait for 10 seconds for the process to completed that why we implement a callback called Callback which takes an object as parameter and this been invoked once the for loop completes counting from 0-9.
There is an important check to see if the callback is not null before invoking it, this handles a situation when callback is not been registered in the other end.
The main method registered the Callaback to display a message into the console before it calls the DoSomething method.

	// Callback class example
	public class CallbackExample
	{
	//define the callback
	public Action<object> Callback;
	public void DoSomething()
	{
	//this task it taking too long call me once done
	for(int i=0;i<10;i++)
	{
	Console.WriteLine("Current counter is {0}",i);
	Thread.Sleep(1000);
	}
	//important to check
	if(Callback != null)
	Callback("Task Completed");
	}
	}
	//main
	void Main()
	{
	CallbackExample _cbe = new CallbackExample();
	_cbe.Callback = (o) => Console.WriteLine(o);
	_cbe.DoSomething();
	}
	//eof

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Assign a Record to a Team in CRM 2011

This sample shows how to assign a record to a team using the AssignRequest message.

	using System;
	using System.ServiceModel;
	using System.ServiceModel.Description;
	// These namespaces are found in the Microsoft.Xrm.Sdk.dll assembly
	// found in the SDK\bin folder.
	using Microsoft.Xrm.Sdk;
	using Microsoft.Xrm.Sdk.Query;
	using Microsoft.Xrm.Sdk.Discovery;
	using Microsoft.Xrm.Sdk.Client;
	using Microsoft.Crm.Sdk.Messages;
	namespace Microsoft.Crm.Sdk.Samples
	{
	///
	/// Demonstrates how to assign a record to a team.
	/// If you want to run this sample repeatedly, you have the option to
	/// delete all the records created at the end of execution.
	///
	public class AssignRecordToTeam
	{
	#region Class Level Members
	///
	/// Stores the organization service interface.
	///
	private OrganizationServiceProxy _serviceProxy;
	private IOrganizationService _service;
	// Define the IDs needed for this sample.
	public Guid _accountId;
	public Guid _teamId;
	public Guid _roleId;
	#endregion Class Level Members
	#region How To Sample Code
	///
	/// Create and configure the organization service proxy.
	/// Create a team, an account and a role.
	/// Add read account privileges to the role.
	/// Assign the role to the team so that they can read the account.
	/// Assign the account to the team.
	/// Optionally delete the account, team and role records.
	/// The friendly name of
	/// the target organization.
	/// The name of the discovery server.
	/// Indicates whether to prompt the user
	/// to delete the records created in this sample.
	///
	public void Run(ServerConnection.Configuration serverConfig, bool promptForDelete)
	{
	try
	{
	// Connect to the Organization service.
	// The using statement assures that the service proxy will be properly disposed.
	using (_serviceProxy = ServerConnection.GetOrganizationProxy(serverConfig))
	{
	// This statement is required to enable early-bound type support.
	_serviceProxy.EnableProxyTypes();
	_service = (IOrganizationService)_serviceProxy;
	// Call the method to create any data that this sample requires.
	CreateRequiredRecords();
	// Assign the account to a team.
	AssignRequest assignRequest = new AssignRequest()
	{
	Assignee = new EntityReference
	{
	LogicalName = Team.EntityLogicalName,
	Id = _teamId
	},
	Target = new EntityReference(Account.EntityLogicalName, _accountId)
	};
	_service.Execute(assignRequest);
	Console.WriteLine("The account is owned by the team.");
	DeleteRequiredRecords(promptForDelete);
	}
	}
	// Catch any service fault exceptions that Microsoft Dynamics CRM throws.
	catch (FaultException)
	{
	// You can handle an exception here or pass it back to the calling method.
	throw;
	}
	}
	///
	/// This method creates any entity records that this sample requires.
	/// Create a team, an account and a role.
	/// Add read account privileges to the role.
	/// Assign the role to the team so that they can read the account.
	/// Assign the account to the team.
	///
	public void CreateRequiredRecords()
	{
	// Instantiate an account entity record and set its property values.
	// See the Entity Metadata topic in the SDK documentation to determine
	// which attributes must be set for each entity.
	Account setupAccount = new Account
	{
	Name = "Example Account"
	};
	// Create the account record.
	_accountId = _service.Create(setupAccount);
	Console.WriteLine("Created {0}", setupAccount.Name);
	// Retrieve the default business unit needed to create the team and role.
	QueryExpression queryDefaultBusinessUnit = new QueryExpression
	{
	EntityName = BusinessUnit.EntityLogicalName,
	ColumnSet = new ColumnSet("businessunitid" ),
	Criteria = new FilterExpression()
	};
	queryDefaultBusinessUnit.Criteria.AddCondition("parentbusinessunitid",
	ConditionOperator.Null);
	BusinessUnit defaultBusinessUnit = (BusinessUnit)_service.RetrieveMultiple(
	queryDefaultBusinessUnit).Entities[0];
	// Instantiate a team entity record and set its property values.
	// See the Entity Metadata topic in the SDK documentation to determine
	// which attributes must be set for each entity.
	Team setupTeam = new Team
	{
	Name = "Example Team",
	BusinessUnitId = new EntityReference(BusinessUnit.EntityLogicalName,
	defaultBusinessUnit.Id)
	};
	// Create a team record.
	_teamId = _service.Create(setupTeam);
	Console.WriteLine("Created {0}", setupTeam.Name);
	// Instantiate a role entity record and set its property values.
	// See the Entity Metadata topic in the SDK documentation to determine
	// which attributes must be set for each entity.
	Role setupRole = new Role
	{
	Name = "Example Role",
	BusinessUnitId = new EntityReference(BusinessUnit.EntityLogicalName,
	defaultBusinessUnit.Id)
	};
	// Create a role record. Typically you would use an existing role that has the
	// the correct privileges. For this sample we need to be sure the role has
	// at least the privilege to read account records.
	_roleId = _service.Create(setupRole);
	Console.WriteLine("Created {0}", setupRole.Name);
	// Create a query expression to find the prvReadAccountPrivilege.
	QueryExpression queryReadAccountPrivilege = new QueryExpression
	{
	EntityName = Privilege.EntityLogicalName,
	ColumnSet = new ColumnSet("privilegeid", "name"),
	Criteria = new FilterExpression()
	};
	queryReadAccountPrivilege.Criteria.AddCondition("name",
	ConditionOperator.Equal, "prvReadAccount");
	// Retrieve the prvReadAccount privilege.
	Entity readAccountPrivilege = _service.RetrieveMultiple(
	queryReadAccountPrivilege)[0];
	Console.WriteLine("Retrieved {0}", readAccountPrivilege.Attributes["name"]);
	// Add the prvReadAccount privilege to the example roles to assure the
	// team can read accounts.
	AddPrivilegesRoleRequest addPrivilegesRequest = new AddPrivilegesRoleRequest
	{
	RoleId = _roleId,
	Privileges = new[]
	{
	// Grant prvReadAccount privilege.
	new RolePrivilege
	{
	PrivilegeId = readAccountPrivilege.Id
	}
	}
	};
	_service.Execute(addPrivilegesRequest);
	Console.WriteLine("Added privilege to role");
	// Add the role to the team.
	_service.Associate(
	Team.EntityLogicalName,
	_teamId,
	new Relationship("teamroles_association"),
	new EntityReferenceCollection() { new EntityReference(Role.EntityLogicalName, _roleId) });
	Console.WriteLine("Assigned team to role");
	// It takes some time for the privileges to propagate to the team. Delay the
	// application until the privilege has been assigned.
	bool teamLacksPrivilege = true;
	while (teamLacksPrivilege)
	{
	RetrieveTeamPrivilegesRequest retrieveTeamPrivilegesRequest =
	new RetrieveTeamPrivilegesRequest
	{
	TeamId = _teamId
	};
	RetrieveTeamPrivilegesResponse retrieveTeamPrivilegesResponse =
	(RetrieveTeamPrivilegesResponse)_service.Execute(
	retrieveTeamPrivilegesRequest);
	foreach (RolePrivilege rp in
	retrieveTeamPrivilegesResponse.RolePrivileges)
	{
	if (rp.PrivilegeId == readAccountPrivilege.Id)
	{
	teamLacksPrivilege = false;
	break;
	}
	else
	{
	System.Threading.Thread.CurrentThread.Join(500);
	}
	}
	}
	return;
	}
	///
	/// Deletes any entity records that were created for this sample.
	/// Indicates whether to prompt the user
	/// to delete the records created in this sample.
	///
	public void DeleteRequiredRecords(bool prompt)
	{
	bool deleteRecords = true;
	if (prompt)
	{
	Console.WriteLine("\nDo you want these entity records deleted? (y/n)");
	String answer = Console.ReadLine();
	deleteRecords = (answer.StartsWith("y") || answer.StartsWith("Y"));
	}
	if (deleteRecords)
	{
	_service.Delete("account", _accountId);
	_service.Delete("team", _teamId);
	_service.Delete("role", _roleId);
	Console.WriteLine("Entity records have been deleted.");
	}
	}
	#endregion How To Sample Code
	#region Main
	///
	/// Main. Runs the sample and provides error output.
	/// Array of arguments to Main method.
	///
	static public void Main(string[] args)
	{
	try
	{
	// Obtain the target organization's Web address and client logon
	// credentials from the user.
	ServerConnection serverConnect = new ServerConnection();
	ServerConnection.Configuration config = serverConnect.GetServerConfiguration();
	AssignRecordToTeam app = new AssignRecordToTeam();
	app.Run(config, true);
	}
	catch (FaultException ex)
	{
	Console.WriteLine("The application terminated with an error.");
	Console.WriteLine("Timestamp: {0}", ex.Detail.Timestamp);
	Console.WriteLine("Code: {0}", ex.Detail.ErrorCode);
	Console.WriteLine("Message: {0}", ex.Detail.Message);
	Console.WriteLine("Plugin Trace: {0}", ex.Detail.TraceText);
	Console.WriteLine("Inner Fault: {0}",
	null == ex.Detail.InnerFault ? "No Inner Fault" : "Has Inner Fault");
	}
	catch (System.TimeoutException ex)
	{
	Console.WriteLine("The application terminated with an error.");
	Console.WriteLine("Message: {0}", ex.Message);
	Console.WriteLine("Stack Trace: {0}", ex.StackTrace);
	Console.WriteLine("Inner Fault: {0}",
	null == ex.InnerException.Message ? "No Inner Fault" : ex.InnerException.Message);
	}
	catch (System.Exception ex)
	{
	Console.WriteLine("The application terminated with an error.");
	Console.WriteLine(ex.Message);
	// Display the details of the inner exception.
	if (ex.InnerException != null)
	{
	Console.WriteLine(ex.InnerException.Message);
	FaultException fe =
	ex.InnerException
	as FaultException;
	if (fe != null)
	{
	Console.WriteLine("Timestamp: {0}", fe.Detail.Timestamp);
	Console.WriteLine("Code: {0}", fe.Detail.ErrorCode);
	Console.WriteLine("Message: {0}", fe.Detail.Message);
	Console.WriteLine("Plugin Trace: {0}", fe.Detail.TraceText);
	Console.WriteLine("Inner Fault: {0}",
	null == fe.Detail.InnerFault ? "No Inner Fault" : "Has Inner Fault");
	}
	}
	}
	finally
	{
	Console.WriteLine("Press to exit.");
	Console.ReadLine();
	}
	}
	#endregion Main
	}
	}

view raw assign a record to a team using the AssignRequest message.cs hosted with ❤ by GitHub