Predicate in .NET

 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

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