C# Flashcards
Late and early binding
Early binding Or Compile time Or static binding: Assigning of object to type reference happens at compile time.
Late binding Or Run time Or Dynamic binding: Assigning of object to type reference happens at run time.
Early binding is efficient while late binding provides flexibility to programmers.
Early binding is best. Because any errors can be resolved at compile time. Late binding is at Run Time
All .Net code have to be cls compliant
Not required. If you want your code to be CLS complaint use the annotation CLScompliant(true)
Answered by: Ravi Kumar on: Dec 3rd, 2011
False All .Net code need not be CLS compliant if you are going to write all modules using single .Net language. However, if you are going to use different .Net language for different modules then you…
Explain what are object oriented language and object based language
Any langauge based on encapsulation concpet and operations with the objects are called as Object Based language. Exmaple : VB is a Object based and not an Object oriented
Any langauge based on encapsulation concept and operations with the objects and also dealing with the inheritance and polymorphism are called as Object Oriented language. Exmaple : C++,C#
Why strings are immutable?
makes it thread safe and
thus imporves performance.
1) In VB6.0 and c++ strings are simple array of bytes, but in .Net it is class System.String and is immutable.
2) A string is a sequential collection of Unicode characters, which usually is used to represent text. A String, on the other hand, is a .NET Framework class (System.String) that represents a Unicode string with a sequential collection of System.Char structure.
String is of reference type which holds an array of char.
string s = “abc”;
internally creates an array of char similar to one below
char[] s = new char[] {‘a’,’b’,’c’};
Arrays are created with definite length and it cannot be dynamically increased.
This is the reason behind immutability in string.
Can you store multiple data types in System.Array?
No
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.
What’s the .NET datatype that allows the retrieval of data by a unique key?
HashTable
What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
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 {}.
Can multiple catch blocks be executed?
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.
Why is it a bad idea to throw your own exceptions?
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.
What’s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
How’s the DLL Hell problem solved in .NET?
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.
What’s a satellite assembly?
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.
What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.
What’s the difference between // comments, /* */ comments and /// comments?
Single-line, multi-line and XML documentation comments.
How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with a /doc switch.
What’s the difference between and <code> XML documentation tag?</code>
Single line code example and multiple-line code example.
Is XML case-sensitive?
Yes, so and are different elements.
What does assert() do?
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.
What’s the difference between the Debug class and Trace class? Documentation looks the same.
Use Debug class for debug builds, use Trace class for both debug and release builds.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
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.
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
What are three test cases you should go through in unit testing?
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).
Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
Explain the three services model (three-tier application).
Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
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.
What’s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.
What is the wildcard character in SQL? 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%’.
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).
Which one is trusted and which one is untrusted?
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.
Why would you use untrusted verificaion?
Web Services might use it, as well as non-Windows applications.
What does the parameter Initial Catalog define inside Connection String?
The database name to connect to.
What does Dispose method do with the connection object?
Deletes it from the memory.
What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
What is the difference between Finalize() and Dispose()?
Dispose() is called by as an indication for an object to release any unmanaged resources it has held.
Finalize() is used for the same purpose as dispose however finalize doesn’t assure the garbage collection of an object.
Dispose() operates determinalistically due to which it is generally preferred.
Is it possible to have different access modifiers on the get/set methods of a property?
No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
If I return out of a try/finally in C#, does the code in the finally-clause run?
Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
Easier in C#. Use if ((object) str1 == (object) str2) { }
How do you mark a method obsolete?
[Obsolete] public int Foo() {…}
or
[Obsolete("This is a message describing why this method is obsolete")] public int Foo() {…}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
