Abstract Classes and Abstract Methods in C#.NET?

http://www.programcall.com/27/csnet/abstract-classes-and-abstract-methods-in-csnet.aspx

http://www.dotnetperls.com/abstract

http://www.c-sharpcorner.com/uploadfile/annathurai/abstract-class-in-c-sharp/

http://www.dotnet-tricks.com/Tutorial/csharp/E0K2011113-A-Deep-Dive-into-C

http://www.onlinebuff.com/article_abstract-class-and-abstract-method-with-an-example-using-c_7.html

http://www.codeproject.com/Articles/6118/All-about-abstract-classes

Difference between Stored Procedure and Function in SQL Server?

Stored Procedures are pre-compile objects which are compiled for first time and its compiled format is saved which executes (compiled code) whenever it is called. But Function is compiled and executed every time when it is called.

Basic Difference

1. Function must return a value but in Stored Procedure it is optional( Procedure can return zero or n values).
2. Functions can have only input parameters for it whereas Procedures can have input/output parameters .
3. Function takes one input parameter it is mandatory but Stored Procedure may take o to n input parameters..
4. Functions can be called from Procedure whereas Procedures cannot be called from Function.

Advance Difference

1. Procedure allows SELECT as well as DML(INSERT/UPDATE/DELETE) statement in it whereas Function allows only SELECT statement in it.
2. Procedures can not be utilized in a SELECT statement whereas Function can be embedded in a SELECT statement.
3. Stored Procedures cannot be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section whereas Function can be.
4. Functions that return tables can be treated as another rowset. This can be used in JOINs with other tables.
5. Inline Function can be though of as views that take parameters and can be used in JOINs and other Rowset operations.
6. Exception can be handled by try-catch block in a Procedure whereas try-catch block cannot be used in a Function.
7. We can go for Transaction Management in Procedure whereas we can't go in Function.

	Stored Procedure	Functions
Compilation	Stored in database in compiled format. Note: Compiled indicates, Execution plan will be made by sql at the time it created and stored in DB.	Will compiled at run time
Return type	It can directly return only integers Return type is not must	It can return any scalar or table Return type is must
Multiple return values	It can also return more than one values (of any data type) indirectly with the help of out parameters	It won't support out parameters
DML Statements	Can have DML statements.	Cannot have DML statements. Note: In case of multi-table valued functions it can contain DML statements affecting Table Variables.
Execution	Stored procedure can execute function. Cannot be the part of Select query as a column. Stored Procedures cannot be used in the SQL statements anywhere in the WHERE/HAVING/SELECT	Function cannot execute stored procedure. Can be the part of select query as a column. Functions be used in the SQL statements anywhere in the WHERE/HAVING/SELECT
Exception handling	Can have Try....Catch	Cannot have Try....Catch

Different Types of SQL Server Functions?

Function is a database object in Sql Server. Basically it is a set of sql statements that accepts only input parameters, perform actions and return the result. Function can return only single value or a table. We can’t use function to Insert, Update, Delete records in the database table(s). 

Types of Function

1. System Defined Function

   These functions are defined by Sql Server for different purpose. We have two types of system defined function in Sql Server

   1. Scalar Function

      Scalar functions operates on a single value and returns a single value. Below is the list of some useful Sql Server Scalar functions.
      System Scalar Function

      Scalar Function

      Description

      abs(-10.67)

      This returns absolute number of the given number means 10.67.

      rand(10)

      This will generate random number of 10 characters.

      round(17.56719,3)

      This will round off the given number to 3 places of decimal means 17.567

      upper('dotnet')

      This will returns upper case of given string means 'DOTNET'

      lower('DOTNET')

      This will returns lower case of given string means 'dotnet'

      ltrim(' dotnet')

      This will remove the spaces from left hand side of 'dotnet' string.

      convert(int, 15.56)

      This will convert the given float value to integer means 15.

   2. Aggregate Function

      Aggregate functions operates on a collection of values and returns a single value. Below is the list of some useful Sql Server Aggregate functions.
      System Aggregate Function

      Aggregate Function

      Description

      max()

      This returns maximum value from a collection of values.

      min()

      This returns minimum value from a collection of values.

      avg()

      This returns average of all values in a collection.

      count()

      This returns no of counts from a collection of values.

2. User Defined Function

   These functions are created by user in system database or in user defined database. We three types of user defined functions.

   1. Scalar Function

      User defined scalar function also returns single value as a result of actions perform by function. We return any datatype value from function.

      
       --Create a table 
      CREATE TABLE Employee
      (
       EmpID int PRIMARY KEY,
       FirstName varchar(50) NULL,
       LastName varchar(50) NULL,
       Salary int NULL,
       Address varchar(100) NULL,
      )
      --Insert Data
      Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(1,'Mohan','Chauahn',22000,'Delhi');
      Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(2,'Asif','Khan',15000,'Delhi');
      Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(3,'Bhuvnesh','Shakya',19000,'Noida');
      Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(4,'Deepak','Kumar',19000,'Noida');
      --See created table
      Select * from Employee 
      
      

      

      
       --Create function to get emp full name 
      Create function fnGetEmpFullName
      (
       @FirstName varchar(50),
       @LastName varchar(50)
      )
      returns varchar(101)
      As
      Begin return (Select @FirstName + ' '+ @LastName);
      end 
      
      

      

      
       --Calling the above created function
      Select dbo.fnGetEmpFullName(FirstName,LastName) as Name, Salary from Employee 
      
      

      

   2. Inline Table-Valued Function

      User defined inline table-valued function returns a table variable as a result of actions perform by function. The value of table variable should be derived from a single SELECT statement.

      
       --Create function to get employees
      Create function fnGetEmployee()
      returns Table
      As
       return (Select * from Employee) 
      
      

      

      
       --Now call the above created function
      Select * from fnGetEmployee() 
      
      

      

   3. Multi-Statement Table-Valued Function

      User defined multi-statement table-valued function returns a table variable as a result of actions perform by function. In this a table variable must be explicitly declared and defined whose value can be derived from a multiple sql statements.

      
       --Create function for EmpID,FirstName and Salary of Employee
      Create function fnGetMulEmployee()
      returns @Emp Table
      (
      EmpID int, 
      FirstName varchar(50),
      Salary int
      )
      As
      begin
       Insert into @Emp Select e.EmpID,e.FirstName,e.Salary from Employee e;
      --Now update salary of first employee
       update @Emp set Salary=25000 where EmpID=1;
      --It will update only in @Emp table not in Original Employee table
      return
      end 
      
      

      

      
       --Now call the above created function
      Select * from fnGetMulEmployee() 
      
      

      

      
       --Now see the original table. This is not affected by above function update command
      Select * from Employee 
      
      

      

Note

1. Unlike Stored Procedure, Function returns only single value.
2. Unlike Stored Procedure, Function accepts only input parameters.
3. Unlike Stored Procedure, Function is not used to Insert, Update, Delete data in database table(s).
4. Like Stored Procedure, Function can be nested up to 32 level.
5. User Defined Function can have upto 1023 input parameters while a Stored Procedure can have upto 2100 input parameters.
6. User Defined Function can't returns XML Data Type.
7. User Defined Function doesn't support Exception handling.
8. User Defined Function can call only Extended Stored Procedure.
9. User Defined Function doesn't support set options like set ROWCOUNT etc.