Expressions and Self Join With Lambda in C#

Expressions with Lambda

Question: What are expressions with Lambda in C#?

In simple terms "It provides the flexibility to pass on an object of type <T> with expecting some results to be retrieved with an instance with Lambda".

Step 1: Create a new WebForm project

Expressions-with-Lambda1.png

Step 2: The complete code of WebForm1.aspx looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="ExpressionApp.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="Expression C#" Font-Bold="true" Font-Size="Large"
                            Font-Names="Verdana" ForeColor="Maroon"></asp:Label>
                    </td>
                </tr>
                <tr>
                    <td>
                        <asp:Label ID="Label6" runat="server" Text="Please Enter FirstNumber" Font-Size="Large"
                            Font-Names="Verdana" Font-Italic="true"></asp:Label>
                    </td>
                    <td>
                        <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td>
                        <asp:Label ID="Label2" runat="server" Text="Please Enter SecondNumber" Font-Size="Large"
                            Font-Names="Verdana" Font-Italic="true"></asp:Label>
                    </td>
                    <td>
                        <asp:TextBox ID="TextBox1" runat="server"></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;
using System.Linq.Expressions;
namespace ExpressionApp
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox4.Text))
            {
                Label5.Text = "Please Enter Some Values";
                Label5.ForeColor = System.Drawing.Color.Red;
            }
            else
            {
                Expression<Func<double, double, double>> obj_Add = (r, q) => r + q; Label5.Text = "The Addition Result is " +
                    obj_Add.Compile()(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text));
                Label5.ForeColor = System.Drawing.Color.Green;
                TextBox1.Text = string.Empty;
                TextBox4.Text = string.Empty;
            }
        }
        protected void Button2_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox4.Text))
            {
                Label5.Text = "Please Enter Some Values";
                Label5.ForeColor = System.Drawing.Color.Red;
            }
            else
            {
                Expression<Func<double, double, double>> obj_Sub = (r, q) => r - q; Label5.Text = "The Substraction Result is " +

                   obj_Sub.Compile()(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text));
                Label5.ForeColor = System.Drawing.Color.Green;
                TextBox1.Text = string.Empty;
                TextBox4.Text = string.Empty;
            }
        }
        protected void Button3_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox4.Text))
            {
                Label5.Text = "Please Enter Some Values";
                Label5.ForeColor = System.Drawing.Color.Red;
            }
            else
            {
                Expression<Func<double, double, double>> obj_Mul = (r, q) => r * q; Label5.Text = "The Multiplication Result is " +
                    obj_Mul.Compile()(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text));
                Label5.ForeColor = System.Drawing.Color.Green;
                TextBox1.Text = string.Empty;
                TextBox4.Text = string.Empty;
            }
        }
        protected void Button4_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox4.Text))
            {
                Label5.Text = "Please Enter Some Values";
                Label5.ForeColor = System.Drawing.Color.Red;
            }
            else
            {
                Expression<Func<double, double, double>> obj_Div = (r, q) => r / q; Label5.Text = "The Division Result is " +
                    obj_Div.Compile()(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text));
                Label5.ForeColor = System.Drawing.Color.Green;
                TextBox1.Text = string.Empty;
                TextBox4.Text = string.Empty;
            }
        }
    }
}

Step 4: The output of the application looks like this:

Expressions-with-Lambda2.png

Step 5: The addition operation output of the application looks like this:

Expressions-with-Lambda3.png

Self Join using Lambda

Question: What is self join using Lambda?

In simple terms "It provides the flexibility to perform a join on a single table and get the result set based on a request query with Lambda operations".

Step 1: Create a new WebForm project

Step 2: The complete code of WebForm1.aspx looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="SelfJoinusingLambdaApp.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">
    <style type
="text/css">
        .grid
        {
            margin-top: 50px;
        }
    </style
>
    <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="Self Join using Lambda" Font-Bold="true"
                            Font-Size="Large" Font-Names="Verdana" ForeColor="Maroon"></asp:Label>
                    </td>
                </tr>
                <tr>
                    <td colspan="2" align="center">
                        <asp:Button ID="Button1" runat="server" Text="Select Data" Font-Names="Verdana" Width="213px"
                            BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />
                    </td>
                </tr>
                <tr>
                    <td colspan="2" align="center">
                        <asp:GridView ID="GridView1" runat="server" CssClass="grid" BackColor="LightGoldenrodYellow"
                            BorderColor="Tan" BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None">
                            <AlternatingRowStyle BackColor="PaleGoldenrod" />
                            <FooterStyle BackColor="Tan" />
                            <HeaderStyle BackColor="Tan" Font-Bold="True" />
                            <PagerStyle BackColor="PaleGoldenrod" ForeColor="DarkSlateBlue" HorizontalAlign="Center" />
                            <SelectedRowStyle BackColor="DarkSlateBlue" ForeColor="GhostWhite" />
                            <SortedAscendingCellStyle BackColor="#FAFAE7" />
                            <SortedAscendingHeaderStyle BackColor="#DAC09E" />
                            <SortedDescendingCellStyle BackColor="#E1DB9C" />
                            <SortedDescendingHeaderStyle BackColor="#C2A47B" />
                        </asp:GridView>
                    </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
SelfJoinusingLambdaApp
{
    public partial class WebForm1 : System.Web.UI.
Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            var query = objEntities.Employee.Join(objEntities.Employee, r => r.ManagerId,
                q => q.EmpId, (r, q) => new{FirstName = r.FirstName,LastName = r.LastName,
                    ManagerName = string.Concat(q.FirstName, " ", q.LastName)});
            GridView1.DataSource = query;
            GridView1.DataBind();}
        #region Instance MembersCompanyEntities objEntities = new CompanyEntities();
        #endregion
    }
}


Step 4: The output of the application looks like this:

Self-Join-using-Lambda1.png

Step 5: The data retrieved output of the application looks like this:

Self-Join-using-Lambda2.png

I hope this article is useful for you. I look forward for your comments and feedback. Thanks Vijay Prativadi


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