Page 7 - ASP.NET 2.0 Interview Questions

Q22. What are data source controls?

A22. Data source controls have no rendering, but instead represent a particular backend data store, for example a database, business object, XML file, or XML Web Service. Data source controls also enable rich capabilities over data - such as sorting, paging, filtering, updating, deleting, and inserting - that data-bound UI controls can automatically use. ASP.NET includes the following server controls out-of-the-box:

SqlDataSource Enables binding to a SQL database represented by an ADO.NET provider, such as Microsoft™ SQL Server, OLEDB, ODBC, or Oracle.
ObjectDataSource Enables binding to a middle-tier object such as a data access layer or business component.
AccessDataSource Enables binding to a Microsoft™ Access (Jet) database.
SiteMapDataSource Enables binding to the hierarchy exposed by an ASP.NET 2.0 site navigation provider.
XmlDataSource Enables binding to an XML file or document.

Q23. What are data bound controls?

A23. Data-bound controls are UI controls that render data as markup to the requesting client device or browser. A data-bound control can auto-bind to data exposed from a data source and will fetch data at the appropriate time in the page request lifecycle. These controls can optionally take advantage of data source capabilities such as sorting, paging, filtering, updating, deleting, and inserting. A data-bound control connects to a data source control through its DataSourceID property.

You may be familiar with some of the data-bound controls in ASP.NET v1.x, such as DataGrid, DataList, Repeater, and list controls like DropDownList. ASP.NET 2.0 contains several new data-bound controls as well, such as:

GridView Renders data in a grid format. This control is an evolution of the DataGrid control, and can automatically take advantage of data source capabilities.
DetailsView Renders a single data item in a table of label/value pairs, similar to the form view in Microsoft™ Access. This control can also automatically take advantage of data source capabilities.
FormView Renders a single data item at a time in a form defined by a custom template. Renders a single data item in a table of label/value pairs, similar to the form view in Microsoft™ Access. This control can also automatically take advantage of data source capabilities.
TreeView Renders data in a hierarchical tree view of expandable nodes.
Menu Renders data in a hierarchical dynamic menu (including flyouts).

Q24. What is a Master Page? How do we use it?

A24. A Master Page is a page that contains markup and controls that should be shared across multiple pages in your site. For example, if all of your pages should have the same header and footer banners or the same navigation menu, you could define this in a Master Page once, and then all pages associated to this Master Page would inherit those common elements. The advantage of defining the header, footer, and navigation in a Master Page is that these elements need only be defined once, instead of multiple times in duplicate code across the pages in your site.

Defining a Master Page is just like defining a normal page. Master Pages can contain markup, controls, or code, or any combination of these elements. However, a Master Page can contain a special type of control, called a ContentPlaceHolder control. A ContentPlaceHolder defines a region of the master page rendering that can be substituted with content from a page associated to the master. A ContentPlaceHolder can also contain default content, just in case the derive page does not need to override this content. The syntax of a ContentPlaceHolder control is given below:

<%-- ContentPlaceHolder control --%>
<asp:contentplaceholder id="FlowerText" runat="server"/>

<%-- ContentPlaceHolder with default content --%>
<asp:contentplaceholder id="FlowerText" runat="server">
  <h3>Welcome to my florist website!</h3>

To differentiate a Master Page from a normal page, a Master Page is saved under the .master file extension. A page can derive from a Master Page by defining a MasterPageFile attribute on its Page directive, as demonstrated below. A page that is associated to a Master Page is called a Content Page.

<%@ Page MasterPageFile="Site.master" %>

Q25. What is a Content Page? How do we use it?

A25. A Content Page can declare Content controls that specifically override content placeholder sections in the Master Page. A Content control is associated to a particular ContentPlaceHolder control through its ContentPlaceHolderID property. A Content Page may only contain markup and controls inside Content controls; it cannot have any top-level content of its own. It can, however, have directives or server-side code.

<%@ Page MasterPageFile="Site.master" %>

<asp:content id="Content1" contentplaceholderid="FlowerText" runat="server">
    Santa Clause will definitely meet you this Christmas!
<asp:content id="Content2" contentplaceholderid="FlowerPicture" runat="server">
    <asp:Image id="image1" imageurl="~/images/santa.jpg" runat="server"/>

Q26. How does Content page access a master page?

A26. In addition to overriding content, it is possible for a Content Page to programmatically access its Master Page. A Content Page creates a strongly-typed reference to the Master Page using the <%@ MasterType %> directive, specifying the virtual path to the master page:

 <%@ MasterType VirtualPath="Site.master" %>

The Content Page can then reference the Master Page using the Master property of the Page class:

Master.FooterText = "This is my custom footer"
Dim adr As AdRotator = Master.FindControl("MyAdRotator")

In the code example above, FooterText is a public property exposed on the Master Page, while MyAdRotator is a control on the Master Page.

Q27. Can we have multiple number of Master pages in an ASP.NET 2.0 web application?

A27. Yes.

Q28. Can we have multiple SiteMapPath controls in an ASP.NET 2.0 web application?

A28. Yes.


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