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

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:

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

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:

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

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