Introduction
Today, in
this article let's play around with one of the interesting and most useful
concept in C#.
Question: What
is predicate?
In simple
terms "It is delegate which accepts a generic type input and returns a boolean
based output".
Step 1: Create
a new WebForm project
![Image1.jpg]()
Step 2: The
complete code of WebForm1.aspx looks like this
<%@
Page Language="C#"
AutoEventWireup="true"
CodeBehind="WebForm1.aspx.cs"
Inherits="PredicateApp.WebForm1"
%>
<!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
id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1"
runat="server">
<center>
<div>
<table>
<tr>
<td
colspan="2"
align="center">
<asp:Label
ID="Label1"
runat="server"
Text="Predicate in C#"
Font-Bold="true"
Font-Size="Large"
Font-Names="Verdana"
ForeColor="Maroon"></asp:Label>
</td>
</tr>
<tr>
<td>
<asp:Label
ID="Label3"
runat="server"
Text="Please Enter First
Number" Font-Size="Large"
Font-Names="Verdana"
Font-Italic="true"></asp:Label>
</td>
<td>
<asp:TextBox
ID="TextBox2"
runat="server"
Width="120px"
Height="22px"></asp:TextBox>
</td>
</tr>
<tr>
<td>
<asp:Label
ID="Label2"
runat="server"
Text="Please Enter
Second Number" Font-Size="Large"
Font-Names="Verdana"
Font-Italic="true"></asp:Label>
</td>
<td>
<asp:TextBox
ID="TextBox1"
runat="server"
Width="120px"></asp:TextBox>
</td>
</tr>
<tr>
<td
colspan="2"
align="center">
<asp:Button
ID="Button1"
runat="server"
Text="Addition"
Font-Names="Verdana"
Width="213px"
BackColor="Orange"
Font-Bold="True"
OnClick="Button1_Click"
/>
</td>
</tr>
<tr>
<td
colspan="2"
align="center">
<asp:Button
ID="Button2"
runat="server"
Text="Substraction"
Font-Names="Verdana"
Width="213px"
BackColor="Orange"
Font-Bold="True"
OnClick="Button2_Click"
/>
</td>
</tr>
<tr>
<td
colspan="2"
align="center">
<asp:Button
ID="Button3"
runat="server"
Text="Multiplication"
Font-Names="Verdana"
Width="213px"
BackColor="Orange"
Font-Bold="True"
OnClick="Button3_Click"
/>
</td>
</tr>
<tr>
<td
colspan="2"
align="center">
<asp:Button
ID="Button4"
runat="server"
Text="Division"
Font-Names="Verdana"
Width="213px"
BackColor="Orange"
Font-Bold="True"
OnClick="Button4_Click"
/>
</td>
</tr>
<tr>
<td
colspan="2"
align="center">
<asp:Label
ID="Label5"
runat="server"
Font-Bold="true"
Font-Names="Verdana"
ForeColor="Maroon"></asp:Label>
</td>
</tr>
</table>
</div>
</center>
</form>
</body>
</html>
Step 3: The
complete code of WebForm1.aspx.cs looks like this
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
namespace
PredicateApp
{
public partial
class WebForm1 : System.Web.UI.Page
{
protected void
Page_Load(object sender,
EventArgs e)
{
TextBox2.Focus();
}
protected void
Button1_Click(object sender,
EventArgs e)
{
if (string.IsNullOrEmpty(TextBox1.Text)
|| string.IsNullOrEmpty(TextBox2.Text))
{
Label5.Text =
"Please Enter Some Values";
Label5.ForeColor = System.Drawing.Color.Red;
}
else
{
double result = +(double.Parse(TextBox2.Text)
+ double.Parse(TextBox1.Text));
Predicate<double>
obj_Add = (double x) => x > 20;
Label5.Text =
"Addition Result is Greater Than 20: " +
obj_Add(result);
Label5.ForeColor = System.Drawing.Color.Green;
TextBox1.Text
= string.Empty;
TextBox2.Text
= string.Empty;
}
}
protected void
Button2_Click(object sender,
EventArgs e)
{
if (string.IsNullOrEmpty(TextBox1.Text)
|| string.IsNullOrEmpty(TextBox2.Text))
{
Label5.Text =
"Please Enter Some Values";
Label5.ForeColor = System.Drawing.Color.Red;
}
else
{
double result = +(double.Parse(TextBox2.Text)
- double.Parse(TextBox1.Text));
Predicate<double>
obj_Sub = (double x) => x > 5;
Label5.Text =
"Subtraction Result is Greater Than 5: " +
obj_Sub(result);
Label5.ForeColor = System.Drawing.Color.Green;
TextBox1.Text
= string.Empty;
TextBox2.Text
= string.Empty;
}
}
protected void
Button3_Click(object sender,
EventArgs e)
{
if (string.IsNullOrEmpty(TextBox1.Text)
|| string.IsNullOrEmpty(TextBox2.Text))
{
Label5.Text =
"Please Enter Some Values";
Label5.ForeColor = System.Drawing.Color.Red;
}
else
{
double result = +(double.Parse(TextBox2.Text)
- double.Parse(TextBox1.Text));
Predicate<double>
obj_Mul = (double x) => x > 20;
Label5.Text =
"Multiplication Result is Greater Than 20: "
+ obj_Mul(result);
Label5.ForeColor = System.Drawing.Color.Green;
TextBox1.Text
= string.Empty;
TextBox2.Text
= string.Empty;
}
}
protected void
Button4_Click(object sender,
EventArgs e)
{
if (string.IsNullOrEmpty(TextBox1.Text)
|| string.IsNullOrEmpty(TextBox2.Text))
{
Label5.Text =
"Please Enter Some Values";
Label5.ForeColor = System.Drawing.Color.Red;
}
else
{
double result = +(double.Parse(TextBox2.Text)
/ double.Parse(TextBox1.Text));
Predicate<double>
obj_Div = (double x) => x > 2;
Label5.Text =
"Division Result is Greater Than 2: " +
obj_Div(result);
Label5.ForeColor = System.Drawing.Color.Green;
TextBox1.Text
= string.Empty;
TextBox2.Text
= string.Empty;
}
}
}
}
Step 4: The
output of the application looks like this:
![Image2.jpg]()
Step 5: The
addition result output of the application looks like this:
![Image3.jpg]()