How to add controls dynamically in windows form c#

Visual studio provide the best features to design the form. By the designer window, you can add the controls from the toolBox. After added the items, you can set the properties by the property window. Same this things, you can do this by the code window. Follow some steps to add controls dynamically.


  Step-1 : Open Code window that is form1.cs file, create a object for controls like

TextBox t1 = new TextBox();

Step-2 : Associate properties of the TextBox class with the current object like

 t1.Name = "Text1";
    t1.Width = 300;
            t1.Text = " Dynamically added Control";
            t1.Location = new Point(10, 10);

Here Point is a class, in which you have to define the coordinates of x-axis and y-axis, where you want to add the TextBox.

Step-3 : Add this instance in the form by following line of code.

 this.Controls.Add(t1);

 Now code Generate the following output:

Design a program to find largest of four numbers

The logic behind the program is, Take four variable like a, b, c, d for numbers also take another variable like large for comparing among three numbers. First of all, assign the value of variable a into the large variable. Compare among three numbers with the large variable. If any one is find larger then you have to assign this variable value into the larger variable.

Example

#include <stdio.h>
#include<conio.h>
main()
{
int a,b,c,d;
int large;

clrscr();
printf("Enter four numbers:\n");
scanf("%d%d%d%d",&a,&b,&c,&d);
large=a;
if(b>large)
large=b;
if(c>large)
large=c;
if(d>large)
large=d;
printf("The largest number is %d",large);
}

Output Of the Given program is

How to draw rectangle in applet

Four coordinate are required For drawing the rectangle in the java applet. First two coordinate define the origin point of the rectangle. Origin point start from upper left corner and further x-coordinate increases width of the rectangle in right side and y-coordinate increases height of the rectangle in downward.

Syntax of drawRect in Java Applet

Graphics_Instance . drawRect(int X1, Int Y1, int Width, int Height);

If you want to set border color of the rectangle then use setColor( ) method of Graphics class, which is exist in java.awt package.

Example - designline.java

import java.awt.*;
import java.applet.*;
public class designline extends Applet
{
int width, height;

   public void init() {
   
      setBackground( Color.gray);
   }

   public void paint( Graphics g ) {

   

      g.setColor( Color.red );
      g.drawRect( 11, 22, 101, 50 );
}
}
First to compile the code and create the class file for this

Prepare the HTML file in the same location with <applet> tag. Like

<applet code="designline" width="400" height="400" />

Save the .html file in same location also run in any browser.

How to draw Line in Applet

Four coordinate are required For drawing the line in the java applet. First two coordinate define the origin point of the line. Origin point start from upper left corner and further x-coordinate increase in right side and y-coordinate increase downward.

Syntax of drawLine in Java Applet

Graphics_Instance . drawLine(int X1, Int Y1, int X2, int Y2);

If you want to set color on line then use setColor( ) method of Graphics class, which is exist in java.awt package.

Example - designline.java

import java.awt.*;
import java.applet.*;
public class designline extends Applet
{
int width,height;
public void init()
{
setBackground(Color.black);

}
public void paint(Graphics g)
{

g.setColor(Color.green);
g.drawLine(0,0,200,200);
}
}

Compilation of Applet code and generate the class file

Prepare the HTML file in the same location with <applet> tag. Like

<applet code="designline" width="400" height="400" />

Save the .html file in same location also run in any browser.

Code Generate the following output

Using the init ( ) method, you can set the back ground color of the applet. Also set the line color using the graphics class. 

Compiling and Running Java Programs

There are various steps to compiling and running java programs, these are
Step-1 : First to install JDK, JRE and JVM into the System.
Step-2 : Prepare source code in any editor like notepad, c++ editor etc.
Step-3:

class HelloWorld
{
public static void main(String r[])
{
int a=10, b=10,c;
c=a+b;
System.out.println("Output of the program is"+c);
}
}

Step-4 : Save the source code in the java bin directory. Class name which contain main method should same of the file name.
Example :  HelloWorld (class name)
                  HelloWorld.java (file name)

Step-5 : Open command prompt and change the directory where your java program has been saved.
Suppose your java software installed in C:/>. Now, compiling steps is:

C:/java/jdk1.7.0/bin> Javac filename.java   (press Enter)
C:/java/jdk1.7.0/bin> Java  filename.java    (press Enter)

Step-6: During compilation, if program generate errors, it means you can't run your program.                 

Execute Batches multiple times using Stored Procedures in SQL

Batches are temporary in nature. To execute a batch more than once, you need to recreate SQL statements and submit them to the server. This leads to an increase in the overhead, as the server needs to compile and create the execution plan for these statements again. Therefore, if you need to execute a batch multiple times, you can save it within a stored procedure. A stored procedure is a precompiled object stored in the database.

Stored procedures can invoke the Data Definition Language (DDL) and Data Manipulation Language (DML) statements and can return values. If you need to assign values to the variables declared in the procedures at the run time, you can pass parameters while executing them. You can also execute a procedure from another procedure. This helps in using the functionality of the called procedure within the calling procedure.

Creating Stored Procedures

You can create a stored procedure by using the CREATE PROCEDURE statement. The syntax of the CREATE PROCEDURE statement is:

CREATE PROCEDURE proc_name
AS
BEGIN
Sql_statement1
Sql_statement2
END

Where Proc_name specifies the name of the stored procedure.

The following example create a stored procedure to view the department names from the Department table:

CREATE PROCEDURE prcDept
AS
BEGIN
SELECT Name FROM HumanResources.Department
END

When the CREATE PROCEDURE statement is executed, the server compiles the procedure and saves it as a database object. The procedure is then available for various applications to execute. The process of compiling a stored procedure involves the following steps:

• The procedure is compiled and its components are broken into various pieces. This process is known as parsing.
• The existence of the referred objects, such as tables and views, are checked. This process is known as resolving.
• The name of the procedure is stored in the sysobjects table and the code that creates the stored procedure is stored in the syscomments table.
• The procedure is compiled and a blueprint for how the query will run is created. This blueprint is specified as execution plan. The execution plan is saved in the procedure cache.
• When the procedure is executed for the first time. The execution plan will be read and fully optimized and then run. The net time the procedure is executed in the same session, it will be read directly from the cache. This increases performance, as there is no repeated compilation.

After creating the stored procedure, you can view the code of the procedure by using the sp_helptext command.

Implementing Triggers and its Types in SQL

In a relational database, data in a table is related to other tables. Therefore, while manipulating data in one table, you need to verify and validate its effect on data in the related tables. In addition, you might need to manipulate data in a table after inserting or updating data in another table.

You also need to ensure that if an error occurs while updating the data in a table, the changes are reverted. This helps in maintaining data integrity. The SQL Server allows you to implement triggers and transactions to maintain data integrity.

This article explains different types of triggers that can be created in SQL Server. Next, we will discusses how to implement triggers to enforce data integrity. Further, we will discuss about how to implement transactions.

Implement Triggers

At times, while performing data manipulation on a database object, you might also need to perform another manipulation on another object. For example, in an organization, the employees use the Online Leave Approval system to apply for leaves. When an employee applies for a leave, the leave details are stored in the Leave-Details table. In addition, a new record is added to the Leaves-For-Approval table. When the supervisors log on to the system, all the leaves pending for their approval are retrieved from the Leaves-For-Approval table and displayed to them.

To perform such operations, the SQL Server allows you to implement triggers. A trigger is a block of code that constitutes a set of T-SQL statements activated in response to certain actions, such as insert or delete. Triggers are used to ensure data integrity before or after performing data manipulations.

Before you implement a trigger, it is important to know the different types of triggers that can be created by using SQL Server.

Identifying Types of Triggers

In the SQL Server, various kinds of triggers can be used for different types of data manipulation operations. The SQL Server supports the following types of triggers:

Data Modification Language (DML) triggers

A DML trigger is fired when data in the underlying table is affected by DML statements, such as INSERT, UPDATE, or DELETE. These triggers help in maintaining consistent, reliable, and correct data in tables. They enable the performance of complex action and cascade these actions to other dependent tables. Cascading is the process of reflecting the changes made in a table in the other related tables.

Data Definition Language (DDL) triggers

A DDL trigger is fired in response to DDL statements, such as CREATE TABLE or ALTER TABLE. DDL triggers can be used to perform administrative tasks, such as database auditing.