A new approach has evolved in Collections ,i.e The LookUp<TKey,TValue>
is one the Class in the Collection which represents a collection of keys each
mapped to one or more values.
We are very familiar with the Dictonary Collection which maps only one value per
key mapping. But when we come across to map the keys with more values, then we
have this LookUp<TKey,TValue>
Where
TKey ----> The types of the keys in the LookUp<TKey,TValue>
TValue ----> The type of the elements of each IEnumerable<T> value in the
LookUp<TKey,TElement>.
I have worked out on this concept to understand the LookUp class. Before going
in deeply, let's create a Custom Class like this
Employee.cs
using System.Collections.Generic;
/// <summary>
/// Summary description for Employee
/// </summary>
public class Employee
{
public int
ID { get; set; }
public string
Email { get; set; }
public int
Age { get; set; }
public string
Name { get; set; }
public bool
MartialStatus { get; set; }
public Employee()
{
//
//
TODO: Add constructor logic here
//
}
}
I have taken an aspx page which I have designed like this:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="LookUpDemo.aspx.cs"
Inherits="LookUpDemo" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html
xmlns="http://www.w3.org/1999/xhtml">
<head
runat="server">
<title>Demo
on Lookup(TKey,TElement) Class</title>
<style
type="text/css">
.rbn
{
font-family: Verdana;
font-size: small;
}
</style>
</head>
<body>
<form
id="form1"
runat="server">
<div>
<asp:GridView
ID="gv1"
runat="server"
BackColor="White"
BorderColor="#CC9966"
BorderStyle="None"
BorderWidth="1px"
CellPadding="4">
<FooterStyle
BackColor="#FFFFCC"
ForeColor="#330099"
/>
<HeaderStyle
BackColor="#990000"
Font-Bold="True"
ForeColor="#FFFFCC"
/>
<PagerStyle
BackColor="#FFFFCC"
ForeColor="#330099"
HorizontalAlign="Center"
/>
<RowStyle
BackColor="White"
ForeColor="#330099"
/>
<SelectedRowStyle
BackColor="#FFCC66"
Font-Bold="True"
ForeColor="#663399"
/>
<SortedAscendingCellStyle
BackColor="#FEFCEB"
/>
<SortedAscendingHeaderStyle
BackColor="#AF0101"
/>
<SortedDescendingCellStyle
BackColor="#F6F0C0"
/>
<SortedDescendingHeaderStyle
BackColor="#7E0000"
/>
</asp:GridView>
<div
class="rbn">
<label
for="rbnList"
style="font-weight:
bold">
Select the Martial Status(Checked Checkboxes are Married)</label>
<asp:RadioButtonList
ID="rbnList"
runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="rbnList_SelectedIndexChanged">
<asp:ListItem
Text="Single"
Value="false"></asp:ListItem>
<asp:ListItem
Text="Married"
Value="true"></asp:ListItem>
</asp:RadioButtonList>
</div>
<br
/>
<asp:GridView
ID="gv2"
runat="server"
CellPadding="4"
ForeColor="#333333"
GridLines="None">
<AlternatingRowStyle
BackColor="White"
/>
<EditRowStyle
BackColor="#2461BF"
/>
<FooterStyle
BackColor="#507CD1"
Font-Bold="True"
ForeColor="White"
/>
<HeaderStyle
BackColor="#507CD1"
Font-Bold="True"
ForeColor="White"
/>
<PagerStyle
BackColor="#2461BF"
ForeColor="White"
HorizontalAlign="Center"
/>
<RowStyle
BackColor="#EFF3FB"
/>
<SelectedRowStyle
BackColor="#D1DDF1"
Font-Bold="True"
ForeColor="#333333"
/>
<SortedAscendingCellStyle
BackColor="#F5F7FB"
/>
<SortedAscendingHeaderStyle
BackColor="#6D95E1"
/>
<SortedDescendingCellStyle
BackColor="#E9EBEF"
/>
<SortedDescendingHeaderStyle
BackColor="#4870BE"
/>
</asp:GridView>
</div>
</form>
</body>
</html>
Here in my example I have taken the Employee Details and I am showing the
employee details in the first grid. Below that I have taken a radio button list
which has two ListItems Called "SINGLE" and "MARRIED".
These ListItems "SINGLE" and "MARRIED" have values as "false" and "true". The
LookUp has keys each mapped to the one or more values. So based on the key
selected the values will be filtered and showed in the below gridview.
"Now, before defining a Lookup Collection, we need to know some basic
fundamentals . Like Dictionary we can not create a Lookup Collection directly.
While creating the instance of the Lookup collection object, we need to invoke
an extension method called ToLookup() which will be returning a Lookup<Tkey,
TElement> object. "
The following code snippet shows creation of a Lookup Collection with key type
of Boolean with Employee Collection.image
![Collections1.gif]()
The output for the two cases is given in the below screen shot
![Collections2.gif]()
-
Filtered based on the
radio button("Married") selected
-
Filtered based on the
Radio Button("Single") Selected.
![Collections3.gif]()
empList.ToLookup(c =>
c.MartialStatus) will pass Lookup<bool, Employee> to employeeLookup Collection.
The Lookup collection is created on key type of Boolean. Hence we can access the
elements as follows,
Happy Coding :-)