Using LINQ Join to combine data
linq
26 Articles
In this article, let's learn about how to use Join in LINQ in .NET.
Note: If you have not done so already, I recommend you read the article on Using LINQ Concat to combine data.
Table of Contents
- Introduction
- Using LINQ Join to combine primitive types
- Using LINQ Join to combine collections using single field
- Using LINQ Join to combine collections using multiple fields
- Summary
Introduction
When working with two collections, we can combine them using LINQ Join() method. This will join elements between two or more collections
and gives a single collection. Join() also know as Equi Join or
Inner Join in SQL. To work with Join(), we need atleast one property in each collection to share
equal value.
LINQ Join() is used to answer questions about collection such as
- Joining collections using common key value to define relationship between them
- Joining Customer and their Orders
- Joining Order and Order Items
Using LINQ Join to combine primitive types
Primitive data types like int, decimal, string, etc can just
combine the values against other equal values in the collection
Code Sample - LINQ Join Primitive Types
Demo - LINQ Join Clause Demo
Let's try LINQ Join with integer type
- Enter number and add it to respective sequence
- For demo purpose I have restricted sequence length to 3
- Click on Join Button to view the result
- Click on reset to try other combination
Joined sequence
| Number | Another Number |
|---|
Using LINQ Join to combine Collections using single field
We can use Join() to combine elements between two or more sequences (arrays, lists, etc.) based on a key value. The result is a new sequence
that contains elements with the matching key and their associated values.
Code Sample - LINQ Join Objects with Single Field
Demo - LINQ Join Clause with Objects Demo
Let's try LINQ Join with Objects
- We have
Productclass with following properties -Id, Name - We have
Saleclass with following properties -Id, Price - The tables are loaded with product and sale collection.
- The Key Expression here is the
Product ID. Join() will combine Products and Sales and return newProductSalecollection. - Click on Join Button to view the result.
- Click on reset to try other combination
| Products | |
|---|---|
| Id | Name |
| 1 | Shirt |
| 2 | Shirt |
| 3 | Shirt |
| 4 | Shirt |
| 5 | Shirt |
| 6 | Shirt |
| Sales | ||
|---|---|---|
| Sale Id | Product Id | Price |
| 123 | 1 | 1000 |
| 789 | 1 | 1000 |
| 456 | 2 | 1000 |
| Sale Id | Product Id | Name | Price |
|---|
Using LINQ Join to combine Collections using multiple fields
So for joining collections with more than one field, the key selector condition will have an anonymous object containing multiple fields to compare.
Code Sample - LINQ Join Objects with Multiple Fields
Demo - LINQ Join Clause with Objects Demo
Let's try LINQ Join with Objects
- We have
Productclass with following properties -Id, Name - We have
Saleclass with following properties -Id, Price - The tables are loaded with product and sale collection.
- The Key Expression here is the
Product IDandProduct Color. Join() will combine Products and Sales and return newProductSalecollection. - Click on Join Button to view the result.
- Click on reset to try other combination
| Products | ||
|---|---|---|
| Id | Name | Color |
| 1 | Shirt | Black |
| 2 | Shirt | Red |
| 3 | Shirt | Black |
| 4 | Shirt | Red |
| 5 | Shirt | Brown |
| 6 | Shirt | White |
| Sales | ||
|---|---|---|
| Sale Id | Product Id | Product Color |
| 123 | 1 | Black |
| 789 | 1 | Red |
| 456 | 2 | White |
| Sale Id | Product Id | Name | Color |
|---|
Summary
In this article we learn't how to combine data between collections using Join. This can be used to combine items between collection
and return a new collection. This can be done using the key selector. We can have single key selector or multiple key selector as anonymous
object. All these can be used with any IEnumerable or IQueryable types.