What is the checked keyword in C#?

The checked keyword is used to control the overflow-checking context for integral-type arithmetic operations and conversions. It can be used as an operator or a statement according to the following forms.
The checked statement:

checked block

The checked operator:

checked (expression)

where:

block

The statement block that contains the expressions to be evaluated in a checked context.

expression

The expression to be evaluated in a checked context. Notice that the expression must be in parentheses ( ).

What is "USING and how to use the "USING" statement.

The following example shows how to use the using statement.

using (Font font1 = new Font("Arial", 10.0f)) 
{
    byte charset = font1.GdiCharSet;
}

---

File and Font are examples of managed types that access unmanaged resources (in this case file handles and device contexts). There are many other kinds of unmanaged resources and class library types that encapsulate them. All such types must implement the IDisposable interface.

As a rule, when you use an IDisposable object, you should declare and instantiate it in a using statement. The using statement calls the Dispose method on the object in the correct way, and (when you use it as shown earlier) it also causes the object itself to go out of scope as soon as Dispose is called. Within the using block, the object is read-only and cannot be modified or reassigned.

The using statement ensures that Dispose is called even if an exception occurs while you are calling methods on the object. You can achieve the same result by putting the object inside a try block and then calling Dispose in a finally block; in fact, this is how the using statement is translated by the compiler. The code example earlier expands to the following code at compile time (note the extra curly braces to create the limited scope for the object):

{
  Font font1 = new Font("Arial", 10.0f);
  try
  {
    byte charset = font1.GdiCharSet;
  }
  finally
  {
    if (font1 != null)
      ((IDisposable)font1).Dispose();
  }
}

Multiple instances of a type can be declared in a using statement, as shown in the following example.

using (Font font3 = new Font("Arial", 10.0f),
            font4 = new Font("Arial", 10.0f))
{
    // Use font3 and font4.
}

You can instantiate the resource object and then pass the variable to the using statement, but this is not a best practice. In this case, the object remains in scope after control leaves the using block even though it will probably no longer have access to its unmanaged resources. In other words, it will no longer be fully initialized. If you try to use the object outside the using block, you risk causing an exception to be thrown. For this reason, it is generally better to instantiate the object in the using statement and limit its scope to the using block.

            Font font2 = new Font("Arial", 10.0f);
            using (font2) // not recommended
            {
                // use font2
            }
            // font2 is still in scope
            // but the method call throws an exception
            float f = font2.GetHeight(); 


Reference:http://msdn.microsoft.com/en-us/library/yh598w02.aspx

Using jQuery and JSON Action methods in MVC

1. jQuery + JSON Action Methods = Cool
   It is easy to return a JSON object instead of a view.

   public JsonResult Create(string CategoryName)
   {
       var category = new Models.Category();
       category.Name = CategoryName;
       category.URLName = CategoryName.ToLower().Replace(" ", "-");
       categoryRepository.Add(category);
       categoryRepository.Save();
   
       return Json(category);
   }

   <script class="str" type="<span">
   "text/javascript" language="javascript">
       $("#CreateNewCategory").click(function() {
           $.getJSON("/category/create/",
                     { "CategoryName": $("#NewCategoryName").val() },
                     CategoryAdded);
                 });
   
                 function CategoryAdded(category) {
                     $("#CategoryList").append("
    + category.URLName + "/cat\">" + category.Name + "
   ");
                 }
   </script>

What is Repository Pattern in ASP.NET MVC?

What is Repository Pattern in ASP.NET MVC?
Repository pattern is usefult for decoupling entity operations form presentation, which allows easy mocking and unit testing.
“The Repository will delegate to the appropriate infrastructure services to get the job done. Encapsulating in the mechanisms of storage, retrieval and query is the most basic feature of a Repository implementation”
“Most common queries should also be hard coded to the Repositories as methods.”
Which MVC.NET to implement repository pattern Controller would have 2 constructors on parameterless for framework to call, and the second one which takes repository as an input:

class myController: Controller

{

    private IMyRepository repository;

 

    // overloaded constructor

    public myController(IMyRepository repository)

    {

        this.repository = repository;

    }

 

    // default constructor for framework to call

    public myController()

    {

        //concreate implementation

        myController(new someRepository());

    }

...

 

    public ActionResult Load()

    {

        // loading data from repository

        var myData = repository.Load();

    }

}

What is difference between Viewbag and Viewdata in ASP.NET MVC?

What is difference between Viewbag and Viewdata in ASP.NET MVC?

The basic difference between ViewData and ViewBag is that in ViewData instead creating dynamic properties we use properties of Model to transport the Model data in View and in ViewBag we can create dynamic properties without using Model data.

How to access Viewstate values of this page in the next page?

How to access Viewstate values of this page in the next page?

PreviousPage property is set to the page property of the nest page to access the viewstate value of the page in the next page.

Page poster = this.PreviousPage;

Once that is done, a control can be found from the previous page and its state can be read.

Label posterLabel = poster.findControl("myLabel");

 string lbl = posterLabel.Text;

How to call javascript function on the change of Dropdown List in ASP.NET MVC?

How to call javascript function on the change of Dropdown List in ASP.NET MVC?
Create a java-script function:

Call the function:

<%:Html.DropDownListFor(x => x.SelectedProduct,

new SelectList(Model.Products, "Value", "Text"),

"Please Select a product", new { id = "dropDown1",

onchange="selectedIndexChanged()" })%>

What is the ‘page lifecycle’ of an ASP.NET MVC?

What is the ‘page lifecycle’ of an ASP.NET MVC?
Following process are performed by ASP.Net MVC page:
1) App initialization
2) Routing
3) Instantiate and execute controller
4) Locate and invoke controller action
5) Instantiate and render view

Remove MVC Action from Cache

For removing the Cache from the action so it get refresh each time, use the below stuff

public class NoCacheAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted ( ActionExecutedContext context )
    {
        context.HttpContext.Response.Cache.SetCacheability( HttpCacheability.NoCache );
    }
}

[HttpGet]
[NoCache]
public JsonResult GetSomeStuff ()
{
    ...
}

What is new in ASP.NET 3.5

ASP.NET AJAX

In ASP.NET 2.0, ASP.NET AJAX was used as an extension to it. You had to download the extensions and install it. However in ASP.NET 3.5, ASP.NET AJAX is integrated into the .NET Framework, thereby making the process of building cool user interfaces easier and intuitive.

The integration between webparts and the update panel is much smoother. Another noticeable feature is that you can now add ASP.NET AJAX Control Extenders to the toolbox in VS2008. Even though this is an IDE specific feature, however I feel it deserves a mention over here for developers, who had to add extenders using source view earlier. It is also worth noting that Windows Communication Foundation (WCF) now supports JSON along with other standard protocols like  SOAP, RSS and POX.

New Controls

The ListView and DataPager are new controls added along with a new datasource control called the LinqDataSource.

ListView

The ListView control is quiet flexible and contains features of the Gridview, Datagrid, Repeater and similar list controls available in ASP.NET 2.0. It provides the ability to insert, delete, page (using Data Pager), sort and edit data. However one feature of the ListView control that stands apart, is that it gives you a great amount of flexibility over the markup generated. So you have a complete control on how the data is to be displayed. You can now render your data without using the tag. You also get a rich set of templates with the ListView control.

DataPager

DataPager provides paging support to the ListView control. The best advantage is that you need not have to keep it ‘tied’ with the control on which the paging is being done. You can keep it anywhere on the page.

DataPager gives you a consistent way of paging with the controls that support it. Currently only ListView supports it as it implements the IPageableItemContainer. However support is likely to be added to other List controls as well.

LINQ

LINQ (Language Integrated Query) adds native data querying capability to C# and VB.NET along with the compiler and Intellisense support. LINQ is a component of .NET 3.5. LINQ defines operators that allow you to code your query in a consistent manner over databases, objects and XML.  The ASP.NET LinqDataSource control allows you to use LINQ to filter, order and group data before binding to the List controls.

ASP.NET Merge Tool

ASP.NET 3.5 includes a new merge tool (aspnet_merge.exe). This tool lets you combine and manage assemblies created by aspnet_compiler.exe. This tool was available earlier as an add-on.

New Assemblies

The new assemblies that would be of use to ASP.NET 3.5 developers are as follows:

·         System.Core.dll - Includes the implementation for LINQ to Objects

·         System.Data.Linq.dll - Includes the implementation for LINQ to SQL

·         System.Xml.Linq.dll - Includes the implementation for LINQ to XML

·         System.Data.DataSetExtensions.dll - Includes the implementation for LINQ to DataSet

·         System.Web.Extensions.dll: Includes the implementation for ASP.NET AJAX (new enhancements added) and new web controls as explained earlier.

Some Other Important Points

1.    ASP.NET 3.5 provides better support to IIS7. IIS7 and ASP.NET 3.5 modules and handlers support unified configuration.

2.    You can have multiple versions of ASP.NET on the same machine.

3.    For those who are wondering what happened to ASP.NET 3.0, well there isn’t anything called ASP.NET 3.0.

4.    VS 2002 worked with ASP.NET 1.0, VS 2003 worked with ASP.NET 1.1, and VS 2005 worked with ASP.NET 2.0. However VS 2008 supports multi-targeting, i.e it works with ASP.NET 2.0, and ASP.NET 3.5.