Wednesday, September 15, 2010

Making assembly visible to a COM component

Following steps are necessary to make an assembly visible to a COM component:

  • Set the Register for COM option under the build configuration
  • Set the ComVisible attribute to true for each class you want exposed
  • Set the ComVisible attribute to false for any class members you want hidden
  • Set the ComVisible attribute to true for any class members that you want visible

Friday, September 10, 2010

Which is fastest While, Do-While, Foreach

Foreach will be faster as it usually maintain no explicit counter, like while and do-while. Foreach essentially say "do this to everything in this set", rather than "do this x times". This will potentially avoid off-by-one errors and make code simpler to read.

Using frequently build assembly in another applications (.Net)

Assume that you are creating a strong named MyAssembly that will be used in several applications. The assembly will be rebuilt frequently during the development cycle. But one must ensure that every time MyAssembly is rebuilt, it works properly with all applications that use it. So, in order to obtain this, we are required to configure the computer on which we develop the assembly such that each application uses the latest build of MyAssembly. To accomplish the above task, take the following action:


  • To point to the build output directory for the strong named assembly, create a DEVPATH environment variable
  • Add the following element to the machine configuration file: <developmentMode developerInstallation="true">. This element tells the CLR to use DEVPATH to locate assembly.

What is a serviced component?

A services component is a .Net component that uses component services of COM+, such as object pooling, transaction management etc. It executes within the managed execution environment of the .Net framework and shares its context with a COM+ application. It enables context sharing between COM+ and .Net framework classes. A serviced component is creates by defining  class that directly or indirectly derives from the ServicesComponent class. It utilizes COM+ services by using attributes of the System.EnterpriseServices namespace. A serviced component should be registered before it can access the component services of COM+. The following three types of registrations are used to register a serviced component:

  • Manual registration: The .Net Framework Service Installation (Regsvcs.exe) tool is used to manually register an assembly containing a serviced component. Manual registration is used for design-time testing to find out the error types that may occur at runtime.
  • Dynamic registration: In dynamic registration, as assembly with a serviced component is copied into the COM+ application's directory. Dynamic registration is used only when a serviced component is created by a managed client.
  • Programmatic registration: Programmatic registration is used to register as assembly containing a serviced component programmatically by creating as instance of the RegistrationHelper class.

Tuesday, September 7, 2010

Covariance and Contravariance feature of .NET 4.0

Hi,
I'll consider below class hierarchy throughout this explanation:

class Account { }
class Savings : Account { }
class Current : Account { }
Now lets begin with Example 1:
class Program
{
delegate T MyDel<T>();
static void Main(string[] args)
{
MyDel<Savings> objSavings = () => new Savings();
MyDel<Account> objAccount = objSavings;
}
}
The code shown in Example 1 will not work in versions prior to 4.0. But if you change generic parameter T to OUT T in 4.0, then this assignment compatibility work via CoVariance. Now check this 4.0 code in Example 2:
class Program
{
delegate T MyDel<out T>();
static void Main(string[] args)
{
MyDel<Savings> objSavings = () => new Savings();
MyDel<Account> objAccount = objSavings;
}
}
The only change in Example 2 is additional OUT keyword.
Now lets move to ContraVariance:
ContraVariance supports the opposite direction of assignment with IN keyword as shown in Example 3:
class Program
{
delegate T MyDel<in T>(T t);
static void Main(string[] args)
{
MyDel<Account> objAccount = (account) => Console.WriteLine(account); MyDel<Savings> objSavings = objAccount;
}
}



These variance come into picture with Generics, Delegates, Interfaces and Collections.

Certain authenticated sharepoint users get "Access Denied" error

When we add our Active Directory groups into Sharepoint site groups, some of the group members receives Access Denied message. This is the problem faced in sharepoint 2007 and doesn't resolve even  individual members of the group are added. So, to get rid of it, just try through following steps:

  • add users in DomainName/UserName format, instead of using just UserName. Avoid adding AD groups directly
  • if you have hosted your site on port 80, and using different name apart from machine name as http://ABC, in this case don't forget to make a entry of your site in Alternate Access Path, under operations tab in central administration.
Hope, this post is helpful to you :)

Friday, September 3, 2010

Lazy initialization – Lazy (.NET 4.0)

With lazy initialization, the memory for an object is not allocated until it is needed. This mainly used to improve performance, reduces unnecessary computations and also reduce memory requirements. This can be useful in following scenarios:

  1. When creation of object is expensive and we want to deferred the creation until it is used.
  2. When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy<Orders> to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
Example:



class MyClass
{
    public string MyData { get; set; }

    public MyClass(string message)
    {
        this.MyData = message;
        Console.WriteLine("  ***  MyClass constructed [{0}]", message);
    }
}



We can declare and use this by creating a lambda expression to pass in our string parameter:
Lazy<MyClass> classInstance = new Lazy<MyClass>(
        () => new MyClass("The message")
    );
We then have access to the IsValueCreated property, which tells us whether or not the instance has been created, as well as the Value property, which will construct and return our actual instance on demand.
Here’s an example showing a complete program using the MyClass above, demonstrating the usage of Lazy<T>:
class Program
{
    static void Main(string[] args)
    {        
        MyClass instance1 = new MyClass("instance1");
        Lazy<MyClass> instance2 = new Lazy<MyClass>(() => new MyClass("instance2"));
        Console.WriteLine("Instances declared");
        Console.WriteLine();
        Console.WriteLine("instance2's MyClass initialized:  {0}", instance2.IsValueCreated);
        Console.WriteLine(); 

        Console.WriteLine("instance1.MyData: {0}", instance1.MyData);
        Console.WriteLine("instance2.MyData: {0}", instance2.Value.MyData);
        Console.WriteLine();
        Console.WriteLine("instance2's MyClass initialized:  {0}", instance2.IsValueCreated);
        Console.ReadKey();
    }
}
The above program, when run, prints out:
***  MyClass constructed [instance1]
Instances declared

instance2's MyClass initialized:  False

instance1.MyData: instance1
  ***  MyClass constructed [instance2]
instance2.MyData: instance2

instance2's MyClass initialized:  True
So, this LAZY type automatically delayed our construction until the first type we accessed it (instance2.Value.MyData).

Use of .NET Framework 4 Client Profile

The .NET Framework 4 Client Profile is a subset of the .NET Framework 4 that is created specifically for client applications(including WinForm, WPF, WCF, and ClickOnce). This enables faster deployment experience by having smaller download sizes and quicker install times. An application that targets the .NET Framework 4 Client Profile has a smaller redistribution package that installs the minimum set of client assemblies on the user's computer, without requiring the full version of the .NET Framework 4 to be present.



When you deploy an application that targets the .NET Framework 4 Client Profile, you only need to deploy the .NET Framework 4 Client Profile. If you are deploying using ClickOnce, you can select the .NET Framework 4 Client Profile as the .NET Framework Launch Condition. 

If you deploy the .NET Framework 4 Client Profile and your application targets the .NET Framework 4, the user will be prompted to install the .NET Framework 4 when he or she tries to run your application.
Source: MSDN

Running applications of earlier versions of .Net framework on framework 4.0

The .NET Framework 4 does not automatically use its version of the CLR to run applications that are built with earlier versions. To run older applications with .NET Framework 4, one must compile their application with the target .NET Framework version specified in the properties for your project in VS, or you can specify the supported runtime with the <supportedRuntime> Element in an App.Config