Call back functions

A callback method is one which is passed as an argument from another method which is invoked due to some kind of event. The 'call back' nature of the argument is that it returns it's result to the method that provided it as an argument - that is to say that it 'calls back' with the return value of the callback method.//An innocuous looking method which will become known as a callback method
//because of the way in which we will invoke it.
int meaningOfLife(void) {
return 42;
}
//An innocuous looking method which just takes an int and prints it to screen
void Print_A_Number(int a_Number) {
System.out.print(a_Number);
}
//invoking a method which passes another method as an argument in reaction to an event (the 'another' method - meaningOfLife - is therefore called a callback method) and the event - main() - is that the program is starting
void main() {
Print_A_Number(meaningOfLife);
}
Callbacks are so-called due to their usage with pointer languages. If you don't use one of those, don't labour over the name 'callback'. Just understand that it is just a name to describe a method that's supplied as an argument to another method, such that when that method is called (whatever condition, such as a button click, a timer tick etc) the callback method is therefore invoked, which returns a result to the calling method, which in turn returns a result to the event.

Call back functions

A callback method is one which is passed as an argument from another method which is invoked due to some kind of event. The 'call back' nature of the argument is that it returns it's result to the method that provided it as an argument - that is to say that it 'calls back' with the return value of the callback method.//An innocuous looking method which will become known as a callback method
//because of the way in which we will invoke it.
int meaningOfLife(void) {
return 42;
}
//An innocuous looking method which just takes an int and prints it to screen
void Print_A_Number(int a_Number) {
System.out.print(a_Number);
}
//invoking a method which passes another method as an argument in reaction to an event (the 'another' method - meaningOfLife - is therefore called a callback method) and the event - main() - is that the program is starting
void main() {
Print_A_Number(meaningOfLife);
}
Callbacks are so-called due to their usage with pointer languages. If you don't use one of those, don't labour over the name 'callback'. Just understand that it is just a name to describe a method that's supplied as an argument to another method, such that when that method is called (whatever condition, such as a button click, a timer tick etc) the callback method is therefore invoked, which returns a result to the calling method, which in turn returns a result to the event.

Best Example for StringBuilder

protected string GetRandomString(int numChars)
{
StringBuilder sb = new StringBuilder();
Random rand = new Random();
for (int i = 0; i < numChars; i++)
{
sb.Append(Convert.ToChar(rand.Next(32, 127)));
}
return (sb.ToString());
}

Attributes and Custom Attributes .Net

Why Attributes? and Custom attributes
Attributes are elements that allow you to add declarative information to your programs. This declarative information is used for various purposes during runtime and can be used at design time by application development tools. For example, there are attributes such as DllImportAttribute that allow a program to communicate with the Win32 libraries. Another attribute, ObsoleteAttribute, causes a compile-time warning to appear, letting the developer know that a method should no longer be used. When building Windows forms applications, there are several attributes that allow visual components to be drag-n-dropped onto a visual form builder and have their information appear in the properties grid. Attributes are also used extensively in securing .NET assemblies, forcing calling code to be evaluated against pre-defined security constraints. These are just a few descriptions of how attributes are used in C# programs.
The reason attributes are necessary is because many of the services they provide would be very difficult to accomplish with normal code. You see, attributes add what is called metadata to your programs. When your C# program is compiled, it creates a file called an assembly, which is normally an executable or DLL library. Assemblies are self-describing because they have metadata written to them when they are compiled. Via a process known as reflection, a program's attributes can be retrieved from its assembly metadata. Attributes are classes that can be written in C# and used to decorate your code with declarative information. This is a very powerful concept because it means that you can extend your language by creating customized declarative syntax with attributes.
This tutorial will show how to use pre-existing attributes in C# programs. Understanding the concepts and how to use a few attributes, will help in finding the multitude of other pre-existing attributes in the .NET class libraries and use them also.

get the permissions of your sql sevrer

SELECT * FROM fn_my_permissions(NULL, 'SERVER');USE AdventureWorks;SELECT * FROM fn_my_permissions (NULL, 'DATABASE');GO

Introduction to Triggers

A trigger is a database object that is attached to a table. In many aspects it is similar to a stored procedure. As a matter of fact, triggers are often referred to as a "special kind of stored procedure." The main difference between a trigger and a stored procedure is that the former is attached to a table and is only fired when an INSERT, UPDATE or DELETE occurs. You specify the modification action(s) that fire the trigger when it is created.
The following shows how to create a trigger that displays the current system time when a row is inserted into the table to which it is attached.


SET NOCOUNT ON
CREATE TABLE Source (Sou_ID int IDENTITY, Sou_Desc varchar(10))
go
CREATE TRIGGER tr_Source_INSERT
ON Source
FOR INSERT
AS
PRINT GETDATE()
go
INSERT Source (Sou_Desc) VALUES ('Test 1')
-- Results --Apr 28 2001 9:56AM

When to Use Triggers
There are more than a handful of developers who are not real clear when triggers should be used. I only use them when I need to perform a certain action as a result of an INSERT, UPDATE or DELETE and ad hoc SQL (aka SQL Passthrough) is used. I implement most of my data manipulation code via stored procedures and when you do this the trigger functionality can be moved into the procedure. For example, let's say you want to send an email to the Sales Manager when an order is entered whose priority is high. When ad hoc SQL is used to insert the Orders row, a trigger is used to determine the OrderPriority and send the email when the criteria is met. The following shows a partial code listing of what this looks like.

SQL SERVER – Insert Values of Stored Procedure in Table – Use Table Valued Function

/* Create Stored Procedure */
CREATE PROCEDURE TestSP
AS
SELECT GETDATE() AS MyDate, 1 AS IntValue
UNION ALL
SELECT GETDATE()+1 AS MyDate, 2 AS IntValue
GO
Traditional Method:
/* Create TempTable */
CREATE TABLE #tempTable (MyDate SMALLDATETIME, IntValue INT)
GO
/* Run SP and Insert Value in TempTable */
INSERT INTO #tempTable (MyDate, IntValue)
EXEC TestSPGO
/* SELECT from TempTable */
SELECT *FROM #tempTable
GO
/* Clean up */
DROP TABLE #tempTable
GO
Alternate Method: Table Valued Function
/* Create table valued function*/
CREATE FUNCTION dbo.TestFn()
RETURNS @retTestFn TABLE
(
MyDate SMALLDATETIME,IntValue INT
)
AS
BEGIN
DECLARE @MyDate SMALLDATETIME
DECLARE @IntValue
INTINSERT INTO @retTestFnSELECT GETDATE() AS MyDate, 1 AS IntValue
UNION ALL
SELECT GETDATE()+1 AS MyDate, 2 AS IntValue
RETURN;
END
GO
/* Select data from Table Valued Function */
SELECT *FROM dbo.TestFn()
GO