C# & Dot Net

Wednesday, September 24, 2014

Difference Between Var & dynamic data type

VAR

Introduced in C# 3.0

Statically typed – This means the type of variable declared is decided by the compiler at compile time.

Need to initialize at the time of declaration.
e.g., var str="string Type";
Looking at the value assigned to the variable str, the compiler will treat the variable str as string.

Errors are caught at compile time.
Since the compiler knows about the type and the methods and properties of the type at the compile time itself.

Visual Studio shows intellisense since the type of variable assigned is known to compiler.

e.g., var Object2;

will throw a compile error since the variable is not initialized. The compiler needs that this variable should be initialized so that it can infer a type from the value.

e.g. var obj1=1;
will compile
var obj1="string Type";

will throw error since the compiler has already decided that the type of obj1 is System.Int32 when the value 1 was assigned to it. Now assigning a string value to it violates the type safety.

Dynamic

Introduced in C# 4.0
Dynamically typed - This means the type of variable declared is decided by the compiler at runtime time.
No need to initialize at the time of declaration.
e.g., dynamic strValue;
strValue=”String Type”; //Works fine and compiles
strValue=100; //Works fine and compiles
Errors are caught at runtime
Since the compiler comes to about the type and the methods and properties of the type at the run time
Intellisense is not available since the type and its related methods and properties can be known at run time only

e.g., dynamic object2;
will compile;
e.g., dynamic object2;
will compile and run
dynamic object2="String Type";

will compile and run since the compiler creates the type for obj1 as System.Int32 and then recreates the type as string when the value “I am a string” was assigned to it.

This code will work fine.

Tuesday, October 2, 2012

Jquery: How to use index()

.index()- returns an integer indicating the position of the passed element relative to the original collection.
-1 means selector or element not found.

Three way to use index()
1.index()

2..index( selector )
selector A selector representing a jQuery collection in which to look for an element.
3..index( element )
element The DOM element or first element within the jQuery object to look for.

Note : Start index is 0(Zero).

more detail- http://api.jquery.com/index

Example

<html>
<head>
  <style>div { font-weight: bold; color: #090; }</style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
  <ul>
  <li id="foo">foo</li>
  <li id="bar">bar</li>
  <li id="baz">baz</li>
</ul>
<div></div>
 <script>

    var listItem = $('#bar');
    $('div').html( 'Index: ' + $('li').index(listItem) );

 </script>
</body>
</html>

Output Demo

Index: 1

Wednesday, August 29, 2012

JQuery:preventDefault() method will do.


e.preventDefault() is the key method, to disable the default operations to proceed further. We first stop the event from further bubbling up to other parent controls and put any custom logic.

@"e" is a event.


Example:
$('#<%=textbox.ClientID%>').bind('cut copy paste',
function (e) {
e.preventDefault();
alert("Cut / Copy / Paste are not allowed.");

});

Tuesday, August 28, 2012

MVC: set Default value in Html.TextboxFor Helper In Asp.Net MVC 2

Html.TextBoxFor in MVC 2 doesn't allow the setting of the value property using the object html attributes.
syntax - 
<%= Html.TextBoxFor(model => model.city, new { maxlength = "40" })%>

If you need to set a default value on a textbox field, you need to use the old 

syntax - 
<%= Html.TextBox("city", "New Delhi", new { maxlength = "40" })%>

Thursday, March 1, 2012

Generic function call

public class clsGeneric
{
public void show<T>(T value)
{
Type t = typeof(T);
Console.WriteLine(t.Name + ":" + value);
}
}

class Program
{
static void Main(string[] args)
{
clsGeneric ng;
ng = new clsGeneric();
int a = 10;
ng.show(a);
string b = "SS";
ng.show(b);

Console.WriteLine("Press any key to close........");
Console.ReadKey();
}
}

OUTPUT
----------------------------
Int32:10
String:SS
Press any key to close........

use global variable with same name of Local variable

public class Demo1
{
int a = 10;
public void ff()
{
int a = 11;
Console.WriteLine("a={0}", this.a);
}

class Program
{
static void Main(string[] args)
{
Demo1 ng = new Demo1();
ng.ff();

Console.WriteLine("Press any key to close........");
Console.ReadKey();

}
}

Output:
-----------------------------------
a=10
Press any key to close........
-----------------------------------

Tuesday, February 14, 2012

Bind generic dictionary collection to combobox

Dictionary<string, string> DicSearch;
DicSearch = new Dictionary<string, string>();
DicSearch.Add("1", "Mohit");
DicSearch.Add("2", "Agrawal");

cboSearch.DataSource = new BindingSource(DicSearch, null);
cboSearch.DisplayMember = "value";
cboSearch.ValueMember = "key";
DicSearch = null;

Tuesday, February 7, 2012

Regular Expression

Regular Express class and validation done himself.

SqlCommand Query based on parameters

SqlCommand command = new SqlCommand();
command.CommandText = "SELECT * FROM Emplyoee emp WHERE emp.Name=@EmpName";
command.Parameters.Add(new SqlParameter(" @EmpName", 50));

// Execute the SQL Server command...
SqlDataReader reader = command.ExecuteReader();
DataTable tblemplyee = new DataTable();
tblemplyee.Load(reader);

foreach (DataRow rowProduct in tblemplyee.Rows)
{
// Use the data...
}

NOTE: This is a good way to block SQL injection

"" vs String.Empty

String.Empty is faster than "" because it doesn't create a new string object instance. Creating new instances brings penalties on both execution speed and memory usage.

Example:

// Slowest

str1 == "";

// Slow

str1.Equals(" ") == false

//Fast

str1 == String.Empty

// Fastest

str1.Equals(String.Empty) == false