Programmer

Value types and Reference types

2012-05-24T10:48:00.001-07:00

Value types and Reference types

Here are the key points:
■ The value of a reference type expression (a variable for example) is a reference,
not an object.
■ References are like URLs—they are small pieces of data that let you access the
real information.
■ The value of a value type expression is the actual data.
■ There are times when value types are more efficient than reference types, and
vice versa.
■ Reference type objects are always on the heap, but value type values can be on
either the stack or the heap, depending on context.
■ When a reference type is used as a method parameter, by default the parameter
is passed by value—but the value itself is a reference.
■ Value type values are boxed when reference type behavior is needed; unboxing
is the reverse process.

Post By : Dipen Shah
Blog By : Dipen Shah

Boxing and Unboxing - c#

2012-05-24T10:43:00.003-07:00

What is concept of Boxing and Unboxing ?

Boxing and unboxing act like bridges between value type and reference types. When we convert

value type to a reference type it’s termed as boxing. Unboxing is just vice-versa. When an object

box is cast back to its original value type, the value is copied out of the box and into the

appropriate storage location.

Example: of boxing and unboxing where integer data type are converted in to object

and then vice versa.

int i = 1;

object obj = i; // boxing

int j = (int) obj; // unboxing

Post By : Urvish Patel

Blog By : Dipen Shah

What is shadowing?

2012-05-22T10:21:00.001-07:00

When two elements in a program have same name, one of them can hide and shadow the other

one. So in such cases the element, which shadowed the main element, is referenced.

Below is a sample code, there are two classes “Parent” and “ShadowedParent”. In

“Parent”, there is a variable “x” which is a integer. “ShadowedParent” overrides

“Parent” and shadows the “x” variable to a string.

Example:

Public Class Parent

Public x As Integer

End Class

Public Class ShadowedParent

Inherits Parent

Public Shadows x As String

End Class

Difference between Shadowing and Overriding:

• Overriding redefines only the implementation while shadowing redefines the whole

element.

• In overriding derived classes can refer the parent class element by using “ME” keyword,

but in shadowing you can access it by “MYBASE”.

Post By : Urvish Patel

Blog By : Dipen Shah

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Retrieving the content of a GridView cell.

2012-05-22T10:17:00.002-07:00

You often need to retrieve the gridview cell content and you write the long code in your code behind.

Below mentioned script are used to retrieve the cell content of gridview on click.

<script language="javascript" type="text/javascript">
$(document).ready(function() {
$("#<%=GridView.ClientID%> tr").filter(":not(:has(table, th))").click(function(e)
{
var $cell = $(e.target).closest("td"); $("#<%=GridView1.ClientID%> td"). removeClass("highlight"); $cell.addClass("highlight"); $("#message").text('You have selected: ' + $cell. text());
});
});
</script>

Post By : Dipen Shah
Blog By : Dipen Shah
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Delete Duplicate Data - SQL

2012-05-21T10:25:00.000-07:00

Delete Duplicate Data without Using primary key and Identity key:

Example:

Id	Name
1	Test
1	Test
1	Test

USE Test

WITH Duplicates AS

(

SELECT Name,Id,

ROW_NUMBER() OVER (PARTITION BY Id,Name ORDER BY Id) AS 'RowNum'

FROM dbo.TestDuplicates

)delete FROM Duplicates WHERE RowNum>1

SELECT * FROM dbo.TestDuplicates

After using this:

Id Name

1 Test

Post By : Urvish Patel

Blog By : Dipen Shah

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Validating CheckboxList using Jquery

2012-05-21T10:04:00.001-07:00

Below script is useful when you want to validate the checkboxlist control.
You just need to add below function on page.

<script language="javascript" type="text/javascript">
function CheckBoxList1_Validation(sender, args)
{
args.IsValid = false;
var cnt = $("#CheckBoxList1 input:checked").length;
args.IsValid = (cnt >= 3);
}
</script>

Post By : Dipen Shah
Blog By : Dipen Shah
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Self Join

2012-05-20T00:27:00.002-07:00

A self-join is simply a normal SQL join that joins one table to itself. This is accomplished by using table name aliases to give each instance of the table a separate name. Joining a table to itself can be useful when you want to compare values in a column to other values in the same column.
A join in which records from a table are combined with other records from the same table when there are matching values in the joined fields. A self-join can be an inner join or an outer join. A table is joined to itself based upon a field or combination of fields that have duplicate data in different records. The data-type of the inter-related columns must be of the same type or needs to cast them in same type.

Examples:

USE ProductManagement

SELECT DISTINCT pv1.ProductID, pv1.CategoryID

FROM dbo.Products pv1

INNER JOIN dbo.Products pv2

ON pv1.ProductID = pv2.ProductID

AND pv1.CategoryID = pv2.CategoryID

ORDER BY pv1.ProductID

Post By : Urvish Patel

Blog By : Dipen Shah

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Get File Name Without Extention

2012-05-19T22:50:00.000-07:00

Below code in asp.net get the filename without extention.

DirectoryInfo directoryInfo = new DirectoryInfo(Environment.GetFolderPath(Environment.SpecialFolder.SendTo)); directoryInfo.GetFiles().Select(file => Path.GetFileNameWithoutExtension(file.Name)).ToArray();

Posted By : Dipen Shah
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Differance Between CLR, CTS, CLS

2012-05-19T22:11:00.000-07:00

What is a CLR? Full form of CLR is Common Language Runtime and it forms the heart of the .NET framework.All Languages have runtime and its the responsibility of the runtime to take care of the code execution of the program. Java has Java Virtual Machine, Similarly .NET has CLR.The responsibilities of CLR are Garbage Collection, Code Access Security, Code Verification, IL( Intermediate language ).
What is a CTS? In order that two language communicate smoothly CLR has CTS (Common Type System). In order that two different languages can communicate Microsoft introduced Common Type System. So “Integer” datatype in VB6 and “int” datatype in C++ will convert it to System.int32 which is datatype of CTS.
What is a CLS(Common Language Specification)? This is a subset of the CTS which all .NET languages are expected to support.Microsoft has defined CLS which are nothing but guidelines that language to follow so that it can communicate with other .NET languages in a seamless manner.
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Always match datatypes in code with the columns in the database

2012-05-19T11:00:00.000-07:00

It's important to make sure that your datatypes match across all layers in your application. For example, if a column's datatype is VarChar(50), you should have the code in queries and stored procedures use local variables of the same datatype.

Similarly, the ADO.NET code in the data layer should specify the same datatype and length.

Posted By : Dipen Shah
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2012-05-19T03:48:00.004-07:00

Difference between Web.Config and Machine.Config File

Machine.Config:
i) This is automatically installed when you install Visual Studio. Net.
ii) This is also called machine level configuration file.
iii)Only one machine.config file exists on a server.
iv) This file is at the highest level in the configuration hierarchy.

Web.Config:
i) This is automatically created when you create an ASP.Net web application project.
ii) This is also called application level configuration file.
iii)This file inherits setting from the machine.config

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ExecuteReader, ExecuteNonQuery and ExecuteScalar

2012-05-19T03:38:00.001-07:00

What is difference between ExecuteReader, ExecuteNonQuery and ExecuteScalar.

ExecuteReader : Use for accessing data. It provides a forward-only, read-only, connected recordset.
ExecuteNonQuery : Use for data manipulation, such as Insert, Update, Delete.
ExecuteScalar : Use for retriving 1 row 1 col. value., i.e. Single value. eg: for retriving aggregate function. It is faster than other ways of retriving a single value from DB.

Posted By : Dipen Shah
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Disallowing cut/copy/paste operations on a TextBox

2012-05-19T03:15:00.007-07:00

Below is the simple jquery to not allow user to cut/copy/paste operations on a TextBox

<script type="text/javascript">
$(document).ready(function() {
$('#<%=txtNewPwd.ClientID%>').bind('cut copy paste',
function(e) {
e.preventDefault();
alert("Cut / Copy / Paste disabled in this textbox");
});
$('#<%=txtConfirmNewPwd.ClientID%>').bind('cut copy
paste', function(e) {
e.preventDefault();
alert("Cut / Copy / Paste disabled in this textbox
too!");
});
});
</script>

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