-->

Sunday, May 18, 2014

How to make Digital clock using ajax in asp.net

Using AJAX Technology you can change time at runtime in asp.net. So you can easily create web development in the asp.net. Here we will take a simple example, which shows time on the webpage also page will refreshed after 1 second .
ScriptManager : The ScriptManager control is the first AJAX server control in the toolbox. This control helps in implementing the ajax functionality in the asp.net website. You need to place this control on the webpage wherever AJAX functionality is required. In the absence of this control, no other Ajax server controls, such as Timer, UpdatePanel and UpdateProgress , can be added to the webpage. The ScriptManager control is responsible for managing client scripts for AJAX-enabled website . The Script Manager control use a ScriptManager class to manage AJAX script libraries and script files.

Timer Control :  Sometimes , there can be a situation when you want to update the contents of the page after a specific interval. for example , there is a web page showing the stock prices where the price of the stock changes frequently. you are asked to update the stock prices after every minute . In this scenario , you need to use the Timer control . The Timer control contains a property named interval and an event named Tick.. The Interval property of the timer control is used to specify the desired time limit in second.
lets take an Example

Copy this code and paste your web form ( Before copy you must add ajax control tool kit to your project )


<%@ Page Language="C#" %>

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

 <script runat="server">

    protected void Timer1_Tick(object sender, EventArgs e)
    {
        Label1.Text = DateTime.Now.ToLongTimeString();
    }
</script>

 <html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <br />
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">

         <ContentTemplate >
            <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
            <asp:Timer ID="Timer1" runat="server" Interval="1000" ontick="Timer1_Tick">
            </asp:Timer>
        
        </ContentTemplate>
        </asp:UpdatePanel>
    
    </div>
    </form>
</body>
</html>


OUTPUT
using ajax make a digital clock in asp.net


Tuesday, May 13, 2014

Create RadioButton list and Access Checked Value in Asp.Net MVC

List of Radio buttons are placed on the view when programmer need to checked only one value among a group by the user. Asp.Net MVC provides some simple steps to complete this task with few lines of code.

First, create an action in the controller and write a single line which will return that on the view. This type of view is called HttpGet method which only used to get the values on the page, in this case we don’t want any value from this action so we are returning only null view.

public ActionResult RadioList()
{
return View();
}

Add a view having the same name as in above action which have four radio buttons of same name and values defined sequentially, as written in below code:

<h2>RadioList</h2>
@using (Html.BeginForm())
{
    <div>
        <ul>
            <li>@Html.RadioButton("radioList", 1) RadioButton 1 </li>
            <li>@Html.RadioButton("radioList", 2) RadioButton 2 </li>
            <li>@Html.RadioButton("radioList", 3) RadioButton 3 </li>
            <li>@Html.RadioButton("radioList", 4) RadioButton 4 </li>
        </ul>

         <input type="submit" value="Submit" id="submitBtn" />
    </div>
}

All of these radio buttons have the same name “radioList” that may be changed. The last line of above code have a submit button which will submit the values of this page to the action written on the same controller and of course same name. This type of method is called HttpPost, written below:

[HttpPost]
public ActionResult RadioList(FormCollection collection)
{
ValueProviderResult result = collection.GetValue("radioList");
string checkedValue = result.AttemptedValue;
return View();
}

The parameter “collection” will have all the values input by the user on the view, now we have to access the checked value of the radiobutton list defined on the view. The class System.Web.Mvc.ValueProviderResult used to represents the result of binding a value (such as from a form post or query string) to an action-method argument property, or to the argument itself.

Create RadioButton list and Access Checked Value in Asp.Net MVC

After getting the value from the collection the checked value is stored in AttemptedValue property of this class’s object. So we have simply accessed the checked value from the view.

Expression Evaluation and Compound Expression in JAVA

As discussed in earlier articles, expressions can either be pure expressions or mixed expressions. Pure expressions have all operands of same datatypes, contrary to mixed expressions that have operands of mixed datatypes.

Evaluating Pure Expressions

Pure expressions produce the result having the same datatypes as that of its operands e.g.

Int a = 5, b = 2, c;
a + b will produce result 7 of int type.
a/b will produce result 2 of int type.
Notice that it will not produce 2.5, it will produce 2.

Evaluating Mixed Expressions

In Java, when a mixed expression is evaluated, it is first divided into component sub-expressions up to the level of two operands and an operator. Then the type of sub-expression is decided keeping in mind general conversion rules. Using the results of sub-expressions, the next higher level of expression is evaluated and its type is determined. This process is continued till you get the final result of the expression.

Boolean (Logical) Expressions

The expressions that result into false or true called Boolean expressions. The Boolean expressions are combination of constants, variables and logical and relational operators. The rule for writing Boolean expressions states :
A Boolean expression may contain just one signed or unsigned variable or a constant, or it may have two or more variable or/and constant, or two or more expressions joined by valid relational and/or logical operators. Two or more variable or operators should not occur in continuation.
The following are examples of some valid Boolean expressions :
(i) x > y (ii) (y + z) >= (x/z)
(iii) (a + b) > c&& (c + d) > a (iv) (y > x) || (z<y)
(v) x||y && z (vi) (x)
(vii) (-y) (viii) (x-y)
(ix) (x > y) && ( !y < z) (x) x <= !y && z

Compound Expression

A compound expression is the one which is made up by combining two or more simple expressions with the help of operator. For example,
(a +b)  / (c +d)
Is a compound expression.
(a > b)  || (b > c)
Is example of another compound expression.

Type Conversion and its Types used in JAVA

An implicit type conversion is a conversion performed by the compiler without programmer’s intervention. An implicit conversion is applied generally whenever differing data types are intermixed in an expression (mixed mode expression), so as not to lose information.

The Java compiler converts all operands up to the type of the largest operand, which is called type promotion. This is done operation by operation, as described in the following type conversion rules
If either operand is of type double, the other is converted to double.

  • Otherwise, if either operand is of type float, the other is converted to float.
  • Otherwise, if either operand is of type long, the other is converted to long.
  • Otherwise, both operands are converted to type int.

Once these conversion rules have been applied, each pair of operands is of same type and the result of each operation is the same as the type of both operands.
The implicit type conversion wherein datatypes are promoted is known as Coercion.
Although coercion exempts the user from worrying about different datatype of operands, yet it has one disadvantage. Coercions decrease the type error detection ability of the compiler. You have already used the implicit type conversion unknowingly. Recall that you use “ “ + <number> (e.g., “ “ +5) to convert it to string.

Explicit type conversion

An explicit type conversion is user-defined that forces an expression to be specific type. The explicit conversion of an operand to a specific Type Casting. Type casting in Java is done as shown below :

(type) expression Where type is a valid Java data type to which the conversion is to be done. For example, to make sure that the expression (x + y/2) evaluates to type float, write it as: (float) (x +y /2)

Casts are often considered as operators. As an operators, a cast is unary and has the same precedence as any other unary operator.

Below is a table that indicates to which of the other primitive types a given primitive data type can be cast. The symbol C indicates that an explicit cast is required since the precision is decreasing. The symbol A indicates that the precision is increasing so an automatic cast occurs without the need for an explicit cast. N indicates that the conversion is not allowed.

Type Conversion and its Types used in JAVA

The * asterisk indicates that the least significant digits, may be lost in the conversion even though the target type allows for bigger numbers. For example, a large value in an int type value that uses all 32 bits will lose some of the lower bits when converted to float since the exponent uses 8 bits of the 32 provided for float value.

Assigning a value to a type with a greater range (e.g. from short to long) poses no problem, however, assigning a value of larger data type to a smaller data type (e.g., from double to float) may result in losing some precision.
Programmer cannot typecast a Boolean type to another primitive type and viceversa. So, we cannot cast a primitive type to an object reference, or viceversa.  

Expressions and its types used in JAVA

An expressions is composed of one or more operations. The objects of the operation(s) are referred to as operands. The operations are represented by operators. Therefore, operators, constants, and variables are the constituents of expressions.

An Expression in Java is any valid combination of operators, constants, and variables are the constituents of Java tokens. The expression in Java can be of any type
  • Arithmetic expression
  • Compound expression
  • Relational (or logical) expression
Type of operators used in an expression determine the expression type. For instance, if an expression is formed using arithmetic operator, it is an arithmetic expression; if an expression has relational and/or Boolean operators, it is a Boolean expression. An arithmetic expression always results in a number (integer or real) and a logical expression always results in a logical value i.e., either true or false.

Arithmetic Expressions

Expressions and its types used in JAVA

Arithmetic expressions can either be pure integer expressions or pure real expressions. Sometimes a mixed expression can also be formed which is a mixture of real and integer expressions.
In pure expressions, all the operands are of same type. And in mixed expressions, the operands are of mixed or different data types.
Integer expressions are formed by connecting integer constants and/or integer variables using integer arithmetic operators.  The following are valid integer expression:

 final int count = 30
int I, J, K, X, Y, Z
– J, K – X, K + X – Y + count, – J + K * Y, J/Z, Z % X

Real expression are formed by connecting real constants and/or real variables using real arithmetic operators. The following are valid real expression:

final float bal = 250.3f:
float qty, amount value;
double fin, inter;

Rule for these arithmetic expressions is the same and it states that:
An arithmetic expression may contain just one numeric variable or a constant, or it may have two or more variables or/and constants, or two or more expressions joined by valid arithmetic operators. Two or more variables or operators should not occur in continuation.

Apart from variables, constants and arithmetic operators, an arithmetic expression may consist of Java’s mathematical functions that are part of Java standard library and are available through Math class defined in java.lang package. The following image lists various math functions that are defined in the Math class of Java.lang package.

You can use these math functions as per following syntax:
Math.Function_name (argument list) ---- The arguments are the values required by a function to work upon. For example, to calculate ab, you may write: math.pow(a, b)

Following are examples of valid arithmetic expressions :
Given     int a, b, c ;  float, p, q, r ; double x, y, z ;
a/b, p/q +a-c, x/y + p*a/b, Math .sqrt (b)*a) – c, Math.ceil (p) + a)/c, Math. Max (c,b) +x/y – z/q +c  

Following are example of invalid arithmetic expressions :
Given int , a, b, c ;  float, p, q, r ;   double x, y, z ;
x + * r      two operators on continuation.
q(a + b – z/4)   operator missing between q and parenthesis.
Math.pow (0, - 1)  Domain error because if base = 0 then exp should not be <= 0.
n *log (-3) + p/q  Domain error because logarithm of negative number is not possible.

How to Update Data in tables: SQL

Programmer need to modify the data in the database when the specifications of a customer, a client, a transaction, or any other data maintained by the organization undergo a change.

For example, if a client changes his address or if the quantity of a product ordered is changed, the required changes need to be made to the respective rows in the tables. You can use the UPDATE statement to make the changes. Updating ensures that the latest and correct information is available at any point of time. One column of a row is the smallest unit of an update.

You can update data in a table by using the UPDATE DML statement. The syntax of the UPDATE statement is:

UPDATE table_name SET column_name = value [, column_name = value]
[FROM table_name]
[WHERE condition]
Where,

  • Table_name specifies the name of the table you have to modify.
  • Column_name specifies the columns you have to modify in the specified table.
  • Value specifies the value(s) with which you have to update the column(s) of the table. Some valid values include an expression, a column name, and a variable name. The DEFAULT and NULL keywords can also be supplied.
  • FROM table_name specifies the table(s) that is used in the UPDATE statement.
  • Condition specifies the rows that you have to update.

Guidelines for Updating Data

You need to consider the following guidelines while updating data:

  • An update can be done on only one table at a time.
  • If an update violates integrity constraints, then the entire update is rolled back.

The following statement updates the AddressLine2 attribute of AddressID 104

UPDATE Address
SET AddressLine2 = ‘Plaza Palace’
WHERE AddressID = 104

Consider another example where you need to update the Title of an employee, Lynn Tsoflias to ‘Sales Executive’, in the Employee table. To perform this task, you need to refer to the contact table to obtain the Contact ID. You can update the details by using the following statement:

UPDATE HumanResources.Employee SET Title = ‘Sales Executive’
FROM HumanResources.Employee e, Person.Contact c
WHERE e.contactID = c.ContactID
AND c.FirstName = ‘Lynn’ and c.LastName = ‘Tsoflias’

When the preceding command is executed, the Title will be changed to ‘Sales Executive’.

Delete data from database and related table.

How to Delete Data from Table or Related Table, SQL

Programmer need to delete data from the database when it is no longer required. The smallest unit that can be deleted from a database is a row. You can delete a row from a table by using the DELETE DML statement. The syntax of the DELETE statement is:

DELETE [FROM] table_name
[FROM table (s)]
[WHERE condition]
Where,

  • Table_name specifies the name of the table from which you have to delete rows.
  • Table_name specifies the name of the table(s) required to set the condition for deletion.
  • Condition specifies the condition that identifies the row(s) to be deleted.

For example, the following statement deletes the address details of AddressID 104 from the Address table:

 DELETE Address
WHERE AddressID = ‘104’

Deleting Data from Related Tables

While deleting records form related tables, you need to ensure that you first delete the records from the table that contain the foreign key and then from the table that contains the primary key.

Consider the example of the Adventure Works. The Employee table contains data of those employees who have retired from the company. This data is not required anymore. This increases the size of the database.

You are required to ensure that this old data is removed from the Employee table. You can delete this data by using the following SQL statement:

DELETE FROM HumanResources.Employee
WHERE BirthDate < dateadd (yy, -60, getdate ())

The database contains tables related to the Employee table. The related tables are HumanResources.EmployeeAddress, HumanResources.EmployeeDepartmentHistory, HumanResources.EmployeePayHistory, and HumanResources.JobCandidate. The EmployeeID attribute in these tables is a foreign key to the EmployeeID attribute of the Employee table. Therefore, the query results in an error. Therefore, you need to delete data from the related tables before executing the preceding DELETE statement.

Deleting All the Records from a Table

As a database developer, you might need to delete all the records from a table. You can do this by using the following DELETE statement:

 DELETE table_name

You can also use the TRUNCATE DML statement. The syntax of the TRUNCATE statement is:
TRUNCATE TABLE table_name
Where,

  • Table_name specifies the name of the table from which you have to delete rows. However, TRUNCATE TABLE is executed faster.

TRUNCATE TABLE does not support the WHERE clause. In addition, the TRUNCATE TABLE statement does no fire a trigger. When truncate is used, the deleted rows are not entered in the transaction log.
For example, the following statement deletes all the records from the Address table:
TRANCATE TABLE Address

Manipulate XML Data and Parsing with XML document.
© Copyright 2013 Computer Programming | All Right Reserved