C# LINQ Join Query Syntax (How It Works For Developers)

Syntax of the LINQ Join Operator

The syntax for the LINQ Join operator is expressive and follows a pattern that resembles SQL joins. The basic syntax is as follows:

var queryResult = 
    from element1 in collection1
    join element2 in collection2 on element1.Key equals element2.Key
    select new { element1, element2 };

var queryResult = 
    from element1 in collection1
    join element2 in collection2 on element1.Key equals element2.Key
    select new { element1, element2 };

In this syntax:

• element1 and element2 are variables representing elements from collection1 and collection2.
• element1.Key and element2.Key are the properties used as the basis for the join operation.
• The equals keyword specifies the condition for the join.
• The select clause creates a new object that combines elements from both collections.

Types of LINQ Joins

LINQ supports several types of joins, including:

1. Inner Join: Returns only the elements that have matching keys in both collections.

   var innerJoin = from customer in customers
                   join order in orders on customer.CustomerID equals order.CustomerID // join orders to customers based on the customer ID key
                   select new { customer.CustomerID, customer.CustomerName, order.OrderID }; // create a new anonymous object based on the objects obtained from the join

   var innerJoin = from customer in customers
                   join order in orders on customer.CustomerID equals order.CustomerID // join orders to customers based on the customer ID key
                   select new { customer.CustomerID, customer.CustomerName, order.OrderID }; // create a new anonymous object based on the objects obtained from the join

   $vbLabelText   $csharpLabel

2. Left Outer Join (Default): Returns all elements from the left collection and the matching elements from the right collection. If no match is found, the result will contain the default value for the right-side elements.

   var leftOuterJoin = from customer in customers
                       join order in orders on customer.CustomerID equals order.CustomerID into customerOrders
                       from co in customerOrders.DefaultIfEmpty()
                       select new { customer.CustomerID, customer.CustomerName, OrderID = co?.OrderID ?? -1 };

   var leftOuterJoin = from customer in customers
                       join order in orders on customer.CustomerID equals order.CustomerID into customerOrders
                       from co in customerOrders.DefaultIfEmpty()
                       select new { customer.CustomerID, customer.CustomerName, OrderID = co?.OrderID ?? -1 };

   $vbLabelText   $csharpLabel

3. Group Join: Group elements from the left collection with matching elements from the right collection.

   var groupJoin = from customer in customers
                   join order in orders on customer.CustomerID equals order.CustomerID into customerOrders
                   select new { customer.CustomerID, customer.CustomerName, Orders = customerOrders };

   var groupJoin = from customer in customers
                   join order in orders on customer.CustomerID equals order.CustomerID into customerOrders
                   select new { customer.CustomerID, customer.CustomerName, Orders = customerOrders };

   $vbLabelText   $csharpLabel

Installing IronPDF: A Quick Start

To begin leveraging the IronPDF library in your C# project, you can easily install the IronPDF NuGet package. Use the following command in your Package Manager Console:

Install-Package IronPdf 

Alternatively, you can search for "IronPDF" in the NuGet Package Manager and install it from there.

Scenario 1: Combining Data Before PDF Generation

If your goal is to combine data from different data sources before initiating the PDF generation process, LINQ Join can be employed independently. Once you have a unified dataset, you can leverage IronPDF to dynamically generate a PDF document based on the integrated data.

Here's a simplified example:

// Assume 'customerOrderInfo' is a result set obtained using LINQ Join
var pdfDocument = new IronPdf.ChromePdfRenderer();
foreach (var entry in customerOrderInfo)
{
    // Use IronPDF to add content to the PDF based on integrated data
    pdfDocument.AddHTML($"<p>Customer ID: {entry.CustomerID}, Order ID: {entry.OrderID}</p>");
}
// Save or render the PDF document as needed
pdfDocument.SaveAs("IntegratedDataDocument.pdf");

// Assume 'customerOrderInfo' is a result set obtained using LINQ Join
var pdfDocument = new IronPdf.ChromePdfRenderer();
foreach (var entry in customerOrderInfo)
{
    // Use IronPDF to add content to the PDF based on integrated data
    pdfDocument.AddHTML($"<p>Customer ID: {entry.CustomerID}, Order ID: {entry.OrderID}</p>");
}
// Save or render the PDF document as needed
pdfDocument.SaveAs("IntegratedDataDocument.pdf");

Explore more ways of PDF document generation and how you can use LINQ Join with IronPDF by visiting the IronPDF Documentation.

Scenario 2: Dynamic Data Integration During PDF Generation

IronPDF allows dynamic content addition to PDF documents, making it possible to integrate data using LINQ Join during the PDF generation process itself. Here, we'll create and order the customer class to represent the real-world application. The data sources can be an SQL database or some structured format, in this case, a list of objects containing a set of data attributes, just like tables in the database. The following example shows a detailed integration of the LINQ Join method with IronPDF as we use HTML Strings for PDF Generation to create the document:

using System;
using System.Collections.Generic;
using System.Linq;
using IronPdf;

class Order
{
    public int OrderID { get; set; }
    public int CustomerID { get; set; }
    // Other order-related properties...
}

class Customer
{
    public int CustomerID { get; set; }
    // Other customer-related properties...
}

class Program
{
    static void Main()
    {
        // Sample orders collection
        var orders = new List<Order>
        {
            new Order { OrderID = 1, CustomerID = 1 },
            new Order { OrderID = 2, CustomerID = 1 },
            new Order { OrderID = 3, CustomerID = 2 },
        };

        // Sample customers collection
        var customers = new List<Customer>
        {
            new Customer { CustomerID = 1 },
            new Customer { CustomerID = 2 },
        };

        var pdfDocument = new ChromePdfRenderer();
        string htmlContent = "<h1>Details generated using LINQ JOIN</h1>";

        // Use join to find customer orders
        var query = from customer in customers
                    join order in orders on customer.CustomerID equals order.CustomerID
                    select new { CustomerID = customer.CustomerID, OrderID = order.OrderID };

        foreach (var result in query)
        {
            // Use IronPDF to dynamically add content to the PDF based on integrated data
            htmlContent += $"<p>Customer ID: {result.CustomerID}, Order ID: {result.OrderID}</p>";
        }

        // Save or render the PDF document as needed
        pdfDocument.RenderHtmlAsPdf(htmlContent)
                   .SaveAs("DynamicIntegratedDataDocument.pdf");
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using IronPdf;

class Order
{
    public int OrderID { get; set; }
    public int CustomerID { get; set; }
    // Other order-related properties...
}

class Customer
{
    public int CustomerID { get; set; }
    // Other customer-related properties...
}

class Program
{
    static void Main()
    {
        // Sample orders collection
        var orders = new List<Order>
        {
            new Order { OrderID = 1, CustomerID = 1 },
            new Order { OrderID = 2, CustomerID = 1 },
            new Order { OrderID = 3, CustomerID = 2 },
        };

        // Sample customers collection
        var customers = new List<Customer>
        {
            new Customer { CustomerID = 1 },
            new Customer { CustomerID = 2 },
        };

        var pdfDocument = new ChromePdfRenderer();
        string htmlContent = "<h1>Details generated using LINQ JOIN</h1>";

        // Use join to find customer orders
        var query = from customer in customers
                    join order in orders on customer.CustomerID equals order.CustomerID
                    select new { CustomerID = customer.CustomerID, OrderID = order.OrderID };

        foreach (var result in query)
        {
            // Use IronPDF to dynamically add content to the PDF based on integrated data
            htmlContent += $"<p>Customer ID: {result.CustomerID}, Order ID: {result.OrderID}</p>";
        }

        // Save or render the PDF document as needed
        pdfDocument.RenderHtmlAsPdf(htmlContent)
                   .SaveAs("DynamicIntegratedDataDocument.pdf");
    }
}

This code utilizes the join keyword that helps find the matching orders for each customer, making the query more concise and expressive.