Monday, August 27, 2012

.NET : Partial Methods

A partial class or struct may contain a partial method. One part of the class contains the signature of the method. An optional implementation may be defined in the same part or another part. If the implementation is not supplied, then the method and all calls to the method are removed at compile time.
Partial methods enable the implementer of one part of a class to define a method, similar to an event. The implementer of the other part of the class can decide whether to implement the method or not. If the method is not implemented, then the compiler removes the method signature and all calls to the method. The calls to the method, including any results that would occur from evaluation of arguments in the calls, have no effect at run time. Therefore, any code in the partial class can freely use a partial method, even if the implementation is not supplied. No compile-time or run-time errors will result if the method is called but not implemented.
A partial method declaration consists of two parts: the definition, and the implementation. These may be in separate parts of a partial class, or in the same part. If there is no implementation declaration, then the compiler optimizes away both the defining declaration and all calls to the method.
// Definition in file1.cs
partial void onNameChanged();

// Implementation in file2.cs
partial void onNameChanged()
  // method body
The Rules:
  • Partial method declarations must begin with the contextual keyword partial and the method must return void.
  • Partial methods can have ref but not out parameters.
  • Partial methods are implicitly private, and therefore they cannot be virtual.
  • Partial methods cannot be extern, because the presence of the body determines whether they are defining or implementing.
  • Partial methods can have static and unsafe modifiers.
  • Partial methods can be generic. Constraints are put on the defining partial method declaration, and may optionally be repeated on the implementing one. Parameter and type parameter names do not have to be the same in the implementing declaration as in the defining one.
  • You can make a delegate to a partial method that has been defined and implemented, but not to a partial method that has only been defined.
Source :

.NET : Extension Method

An Extension method is a new language feature of C# starting with the 3.0 specification, as well as Visual Basic.NET starting with 9.0. Extension methods enable you to "add" methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. An extension method is a static method of a static class that you can call as though it were an instance method of a different class. 
For example, you could create an extension method named ToDouble that is a static method in a static class you create named StringConversions, but that is called as though it were a method of an object of type string.
Extension Method Declarations and Invocations:
Specifying a method’s first argument with the this keyword modifier will make that method an extension method. The extension method will appear as an instance method of any object with the same type as the extension method’s first argument’s data type. For example, if the extension method’s first argument is of type string, the extension method will appear as a string instance method and can be called on any string object. Also, extension methods can only be declared in static classes.
Example of an extension method:
namespace Netsplore.Utilities
    public static class StringConversions
        public static doubleToDouble(this string s)
            return Double.Parse(s);
        public static boolToBool(this string s)
            return Boolean.Parse(s);
Here both the class and every method it contains are static. ToDouble is an extension method, because method is static and its first argument specifies the this keyword.
Calling an extension method:
    double pi = "3.1415926535".ToDouble();
This produces the following results:
Extension Method Precedence:
Normal object instance methods take precedence over extension methods when their signature matches the calling signature. Extension methods seem like a really useful concept, especially when you want to be able to extend a class you cannot, such as a sealed class or one for which you do not have source code. The previous extension method examples all effectively add methods to the string class. Without extension methods, you couldn’t do that because the string class is sealed.

Thursday, August 23, 2012

T-SQL Syntax

Recently I have came across very good question on
Different T-SQL constructs can assign a value to a regular identifier with a leading '@' without using SET nor SELECT :
  1. An Input argument to a Procedure or Function -
  2. An Output argument to a Procedure -
  3. EXECUTE a Function: EXEC @return = udfFunct() -
  4. The Stored Procedure return status: EXEC @status = uspProc (This is very different from a Function return.) -
  5. The OUTPUT clause: OUTPUT INTO @tablevar (Could count this 4 times but it is really one construct)
  6. RECEIVE .... FROM INTO @tablevar -
  7. FETCH NEXT FROM cursor INTO @varname -
  8. DECLARE @varname INT = 0; -

Wednesday, August 8, 2012

WCF Endpoints : Addresses

All communication with a Windows Communication Foundation (WCF) service occurs through the endpoints of the service. Endpoints provide clients access to the functionality offered by a WCF service.
Each endpoint consists of four properties:
  • An address that indicates where the endpoint can be found.
  • A binding that specifies how a client can communicate with the endpoint.
  • A contract that identifies the operations available.
  • A set of behaviours that specify local implementation details of the endpoint.
In WCF, every service is associated with a unique address. The address provides two important elements: the location of the service and the transport protocol, or transport scheme, used to communicate with the service. The location portion of the address indicates the name of the target machine, site, or network; a communication port, pipe, or queue; and an optional specific path, or URI (Universal Resource Identifier). A URI can be any unique string, such as the service name or a globally unique identifier (GUID).
WCF supports the following transport schemes:
  • TCP
  • IPC
  • Peer network
  • MSMQ
  • Service bus
Addresses always have the following format:
    [base address]/[optional URI]
The base address is always in this format:
    [transport]://[machine or domain][:optional port]
Here are a few sample addresses:

TCP Addresses
TCP addresses use net.tcp for transport and typically include a port number, as in:
When a port number is not specified, the TCP address defaults to port 808:
It is possible for two TCP addresses (from the same host) to share a port:
You can configure TCP-based addresses from different service hosts to share a port.

HTTP Addresses
HTTP addresses use http for transport and can also use https for secure transport. You typically use HTTP addresses with outward-facing Internet-based services, and you can specify a port as shown here:
If you do not specify the port number, it defaults to 80 (and port 443 for HTTPS). As with TCP addresses, two HTTP addresses from the same host can share a port, even on the same machine.

IPC Addresses
IPC (Inter-Process Communication) addresses use net.pipe for transport, to indicate the use of the Windows named pipe mechanism. In WCF, services that use IPC can only accept calls from the same machine. Consequently, you must specify either the explicit local machine name or localhost for the machine name, followed by a unique string for the pipe name:
You can open a named pipe only once per machine, so it is not possible for two named pipe addresses to share a pipe name on the same machine.

MSMQ Addresses
MSMQ addresses use net.msmq for transport, to indicate the use of the Microsoft Message Queue (MSMQ). You must specify the queue name. When you’re dealing with private queues, you must also specify the queue type, but you can omit that for public queues:

Service Bus Addresses
Windows Azure AppFabric Service Bus addresses use sb, http, or https for transport, and must include the service bus address along with the service namespace, for example: