Where
operator comes under
the category of Restriction operator.
It use when we want information on based on condition. Suppose we want products
that have weight more than 100gm. That for we use Where operator for filtering
rows. So there are step first Create a list than use that list with Where
operator:
Step 1 Create a generic list
List collection
in the .NET Framework, which is located in the System.Collections.Generic
namespace. We can say that Lists are
dynamic array in C#. we need < and > for list declaration. Advantage of List<T>
comparison ArrayList is that List<T> can grow and shrinks as the number of
stored objects changes.
Illustrate with an Example
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Web;
namespace
RestrictionOperator
{
public class
Product
{
//Variable declaration
string m_produtct =
string.Empty;
int m_unit = 0;
///
<summary>
///
Name of Product
///
</summary>
public string
ProductName
{
set { m_produtct =
value; }
get { return
m_produtct; }
}
///
<summary>
///
How many units of products
///
</summary>
public int
Unit
{
set { m_unit =
value; }
get { return
m_unit; }
}
///
<summary>
///
Constructor of Product class That contain Name and Units of a product
///
</summary>
///
<param name="ProductName"></param>
///
<param name="Unit"></param>
public Product(string
ProductName, int Unit)
{
this.ProductName = ProductName;
this.Unit = Unit;
}
///
<summary>
///
Another Constrator that contain only Product name
///
</summary>
///
<param name="ProductName"></param>
public Product(string
ProductName)
{
this.ProductName = ProductName;
}
///
<summary>
///
Genarte a list of product with or without quantity
///
</summary>
///
<returns></returns>
public static
List<Product>
GetProduct()
{
List<Product>
ProductList = new
List<Product>();//Name
of product List
ProductList.Add(new
Product("Book",
1));//Add product with Unit
ProductList.Add(new
Product("Pen"));//Add
product without unit
ProductList.Add(new
Product("Pensil"));
ProductList.Add(new
Product("Paper",
20));
return ProductList;
}
}
}
Step 2: Using Where operator
Here we access our previous create List and apply Where operator
for access products.
Illustrate with an Example
using
System;
using
System.Collections.Generic;
using
System.Linq;
using System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
namespace
RestrictionOperator
{
public partial
class
ListExample : System.Web.UI.Page
{
protected
void Page_Load(object
sender, EventArgs e)
{
List<Product>
produ = Product.GetProduct();//Create
product list
var prod =
from pro in
produ where pro.Unit>0
select pro;/*
where condition Check product unit
* * greater than 0*/
//Retrive
product information
foreach (var
p in prod)
{
Response.Write("<b>Product Name</b> "
+ p.ProductName +"
<b> Product Unit :</b>"+p.Unit+ "<br/>");
}
}
}
}
Output:
Product Name Book Product Unit :1
Product Name Paper Product Unit :20