ASP.NET Interview Questions - 3

1. What base class do all Web Forms inherit from?

The Page class.

2. Name two properties common in every validation control?

ControlToValidate property and Text property.

3. What tags do you need to add within the asp:datagrid tags to bind columns manually?

Set AutoGenerateColumns Property to false on the datagrid tag.

4. What tag do you use to add a hyperlink column to the DataGrid?

5. What is the transport protocol you use to call a Web service?

SOAP is the preferred protocol.

6. True or False: A Web service can only be written in .NET?
False

7. What does WSDL stand for?

(Web Services Description Language)

9. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?

DataTextField property

10. Which control would you use if you needed to make sure the values in two different controls matched?

CompareValidator Control

11. True or False: To test a Web service you must create a windows application or Web application to consume this service?

False, the webservice comes with a test page and it provides HTTP-GET method to test.

12. How many classes can a single .NET DLL contain?
It can contain many classes.

ASP.NET Interview Questions - 2

1. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?

Server.Transfer is used to post a form to another page. Response.Redirect is used to redirect the user to another page or site.

2. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?

· A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
· A DataSet is designed to work without any continuing connection to the original data source.
· Data in a DataSet is bulk-loaded, rather than being loaded on demand.
· There's no concept of cursor types in a DataSet.
· DataSets have no current record pointer You can use For Each loops to move through the data.
· You can store many edits in a DataSet, and write them to the original data source in a single operation.
· Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.


3. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?

This is where you can set the specific variables for the Application and Session objects.


4. If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users?

Maintain the login state security through a database.


5. Can you explain what inheritance is and an example of when you might use it?

When you want to inherit (use the functionality of) another class. Base Class Employee. A Manager class could be derived from the Employee base class.


6. Whats an assembly?

Assemblies are the building blocks of the .NET framework.


7. Explain what a diffgram is, and a good use for one?

The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. For reading database data to an XML file to be sent to a Web Service.


8. Whats MSIL, and why should my developers need an appreciation of it if at all?

MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL.


9. Which method do you invoke on the DataAdapter control to load your generated dataset with data?

The .Fill() method


10. Can you edit data in the Repeater control?

No, it just reads the information from its data source


11. Which template must you provide, in order to display data in a Repeater control?

ItemTemplate


12. How can you provide an alternating color scheme in a Repeater control?

Use the AlternatingItemTemplate


13. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?

You must set the DataSource property and call the DataBind method.

ASP.NET Interview Questions - 1

1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process.

inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.

2. What’s the difference between Response.Write() andResponse.Output.Write()?

The latter one allows you to write formattedoutput.

3. What methods are fired during the page load?

Init() - when the pageis instantiated, Load() - when the page is loaded into server memory,PreRender() - the brief moment before the page is displayed to the user asHTML, Unload() - when page finishes loading.

4. Where does the Web page belong in the .NET Framework class hierarchy?

System.Web.UI.Page

5. Where do you store the information about the user’s locale?

System.Web.UI.Page.Culture

6. What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?

CodeBehind is relevant to Visual Studio.NET only.

7. What’s a bubbled event?

When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

8. Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler?

It’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add("onMouseOver","someClientCode();")

9. What data type does the RangeValidator control support?

Integer,String and Date.

10. Explain the differences between Server-side and Client-side code?

Server-side code runs on the server. Client-side code runs in the clients’ browser.

11. What type of code (server or client) is found in a Code-Behind class?

Server-side code.

12. Should validation (did the user enter a real date) occur server-side or client-side? Why?

Client-side. This reduces an additional request to the server to validate the users input.

13. What does the "EnableViewState" property do? Why would I want it on or off?

It enables the viewstate on the page. It allows the page to save the users input on a form.

C# Interview Questions -6

Question Can you change the value of a variable while debugging a C# application?
Answer: Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

Question Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).

Question What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Answer: SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
Question What’s the role of the DataReader class in ADO.NET connections?
Answer: It returns a read-only dataset from the data source when the command is executed.

Question What is the wildcard character in SQL?
Answer: Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.

Question Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).

Question What connections does Microsoft SQL Server support?

Answer: Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).

Question Which one is trusted and which one is untrusted?
Answer: Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.

Question Why would you use untrusted verificaion?
Answer: Web Services might use it, as well as non-Windows applications.

Question What does the parameter Initial Catalog define inside Connection String? The database name to connect to.

Question What’s the data provider name to connect to Access database?
Answer: Microsoft.Access.

Question What does Dispose method do with the connection object?
Answer: Deletes it from the memory.

Question What is a pre-requisite for connection pooling?
Answer: Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

C# Interview Questions -5

Question What’s the difference between and XML documentation tag?
Answer: Single line code example and multiple-line code example.

Question Is XML case-sensitive?
Answer: Yes, so and are different elements.

Question What debugging tools come with the .NET SDK?
Answer: CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

Question What does the This window show in the debugger?
Answer: It points to the object that’s pointed to by this reference. Object’s instance data is shown.

Question What does assert() do?
Answer: In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

Question What’s the difference between the Debug class and Trace class?
Answer: Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

Question Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
Answer: The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.

Question Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.

Question How do you debug an ASP.NET Web application?

Answer: Attach the aspnet_wp.exe process to the DbgClr debugger.

Question What are three test cases you should go through in unit testing?
Answer: Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).

C# Interview Questions -4

Question What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
Answer: A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.

Question Can multiple catch blocks be executed?
Answer: No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

Question Why is it a bad idea to throw your own exceptions?
Answer: Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.

Question What’s a delegate?
Answer: A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

Question What’s a multicast delegate?
Answer: It’s a delegate that points to and eventually fires off several methods.

Question How’s the DLL Hell problem solved in .NET?
Answer: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.

Question What are the ways to deploy an assembly?
Answer: An MSI installer, a CAB archive, and XCOPY command.



Question What’s a satellite assembly?
Answer: When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.

Question What namespaces are necessary to create a localized application?
Answer: System.Globalization, System.Resources.

Question What’s the difference between // comments, /* */ comments and /// comments?
Answer: Single-line, multi-line and XML documentation comments.

Question How do you generate documentation from the C# file commented properly with a command-line compiler?
Answer: Compile it with a /doc switch.

C# Interview Questions -3

Question What’s the difference between an interface and abstract class?
Answer: In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

Question How can you overload a method?
Answer: Different parameter data types, different number of parameters, different order of parameters.

Question If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Answer: Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

Question What’s the difference between System.String and System.StringBuilder classes?
Answer: System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

Question What’s the advantage of using System.Text.StringBuilder over System.String?
Answer: StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.

Question Can you store multiple data types in System.Array?
Answer: No.

Question What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
Answer: The first one performs a deep copy of the array, the second one is shallow.

Question How can you sort the elements of the array in descending order?
Answer: By calling Sort() and then Reverse() methods.

Question What’s the .NET datatype that allows the retrieval of data by a unique key?
Answer: HashTable.

Question What’s class SortedList underneath?
Answer: A sorted HashTable.

Question Will finally block get executed if the exception had not occurred?
Answer: Yes.