Friday, February 29, 2008

C# - interview questions

How many classes can a single.NET DLL contain?
One or more

What are good ADO.NET object(s) to replace the ADO Recordset object?
The differences includes
In ADO, the in-memory representation of data is the Recordset.
In, it is the dataset

A recordset looks like a single table in ADO
In contrast, a dataset is a collection of one or more tables in

ADO is designed primarily for connected access the disconnected access to the database is used

In ADO you communicate with the database by making calls to an OLE DB provider.
In ADO.NET you communicate with the database through a data adapter (an OleDbDataAdapter, SqlDataAdapter, OdbcDataAdapter, or OracleDataAdapter object), which makes calls to an OLE DB provider or the APIs provided by the underlying data source.

In ADO you cant update the database from the recordset. ADO.NET the data adapter allows you to control how the changes to the dataset are transmitted to the database.

On order to get assembly info which namespace we should import?
System.Reflection Namespace

How do you declare a static variable and what is its lifetime? Give an example.

The static modifier is used to declare a static member, which belongs to the type itself rather than to a specific object. The static modifier can be used with fields, methods, properties, operators, events and constructors, but cannot be used with indexers, destructors, or types. In C#, the static keyword indicates a class variable. In VB, the equivalent keyword is Shared. Its scoped to the class in which it occurs.

a. Static int var //in
b. static void Time( ) //in

How do you get records number from 5 to 15 in a dataset of 100 records? Write code.
DataSet ds1=new DataSet();
String strCon=”data source=IBM-6BC8A0DACEF;initial catalog=pubs;integrated security=SSPI;persist” +” security info=False;user
id=sa;workstation id=IBM-6BC8A0DACEF;packet size=4096?;

String strCom1=”SELECT * FROM employee”;
SqlDataAdapter sqlDa1=new SqlDataAdapter(strCom1,strCon);
DataGrid dg1.DataSource=ds1.Tables[”employee”].DefaultView;

OleDbDataAdapter1.Fill(DataSet21, 5, 15, “tab”)
This will fill the dataset with the records starting at 5 to 15

How do you call and execute a Stored Procedure in .NET? Give an example.
ds1=new DataSet();

sqlCon1=new SqlConnection(connectionstring);

String strCom1=”byroyalty”;

sqlCom1=new SqlCommand(strCom1,sqlCon1);
sqlDa1=new SqlDataAdapter(sqlCom1);
SqlParameter myPar=new SqlParameter(”@percentage”,SqlDbType.Int);
sqlCom1.Parameters.Add (myPar);


Dim cn as new OleDbConnection ( “Provider=Microsoft.Jet.OLEDB.4.0;”+ _
“Data Source=C:\Documents and Settings\User\My Documents\Visual Studio Projects\1209\db1.mdb”+ _
“User ID=Admin;”+ _
Dim cmd As New OleDbCommand(”Products”, cn)
cmd.CommandType = CommandType.StoredProcedure

Dim da As New OleDataAdapter(cmd)
Dim ds As New DataSet()
da.Fill(ds, “Products”)
DataGrid1.DataSource = ds.Tables(”Products”)

What is the maximum length of a varchar in SQL Server?
Null-terminated Unicode character string of length n,
with a maximum of 255 characters. If n is not supplied, then 1 is assumed.


The business logic is the aspx.cs or the aspx.vb where the code is being written. The presentation logic is done with .aspx extention.

How do you define an integer in SQL Server?
We define integer in Sql server as
var_name int

How do you separate business logic while creating an ASP.NET application?
There are two level of debugging
1. Page level debugging
For this we have to edit the page level debugging enable the trace to true in the line in the html format of the page.

%@ Page Language=”vb” trace=”true”AutoEventWireup=”false” Codebehind=”WebForm1.aspx.vb” Inherits=”WebApplication2.WebForm1?>

2. You can enable the debugging in the application level for this
Edit the following trace value in web.config file

Enable trace enabled=true.

If there is a calendar control to be included in each page of your application, and and we do not intend to use the Microsoft-provided calendar control, how do you develop it? Do you copy and paste the code into each and every page of your application?
Create the Calendar User Control
The control we will create will contain a calendar control and a label which has the corresponding date and time written
Steps are:-

Creating a CalenderControl
1) To begin, open Visual Studio .NET and begin a new C# Windows Control Library.
2) You may name it whatever you like, for this sample the project name will be CalenderControl

Using the Calender Control in a Windows Application
It’s just like adding any other control like a button or a label.
1) First, create a new Windows Application project named: CustomControl.
2) Add a reference to the Calender Control DLL named: CalenderControl.dll.
3) Now you a can customize the Toolbox:
Right-Click the Toolbox> .NET Framework Components> Browse> select the CalenderControl.dll.
4)The Calender Control is now added to the Toolbox and can be inserted in Windows Form as any other control. The control itself will take care of the date display