Using LINQ Intersect to Find Common data
LINQ
26 Articles
In this article, let's learn about how to use Intersect
in LINQ
in .NET.
Note: If you have not done so already, I recommend you read the article on Using LINQ Except to Find Difference in data.
Table of Contents
- Introduction
- Using LINQ Intersect to compare primitive types
- Using LINQ Intersect to compare objects
- Using LINQ Intersect to compare with Equality Comparer
- Using LINQ Intersect By to compare objects with primitive types
- Using LINQ Intersect By to compare objects
- Summary
Introduction
When working with two collections, we can find the same data between them using LINQ Intersect()
method. The idea here is to find out
values in one which is in other and returns the list of common ones. With Intersect()
, we can compare two collections for Common items.
Intersect()
and IntersectBy()
are exact opposite of Except()
and ExceptBy()
.
LINQ Intersect()
is used to answer questions about collection such as
- Find phones that have sales
- Find customers who have ordered specific product
- Compare data in tables between different environments
Using LINQ Intersect to compare primitive types
Primitive data types like int
, decimal
, string
, etc can just
compare the values against other value in the collection
Code Sample - LINQ Intersect Primitive Types
Demo - LINQ Intersect Clause Demo
Let's try LINQ Intersect with integer type
- Enter number and add it to respective sequence
- For demo purpose I have restricted sequence length to 3
- Click on Intersect Button to view the result
- Click on reset to try other combination
Common :
Using LINQ Intersect to compare objects
Intersect checks for reference equality of two objects for object
data types.
Code Sample - LINQ Intersect Objects
Demo - LINQ Intersect Clause Objects Demo
Let's try LINQ Intersect with objects
- We have
Product
class with following properties -Id, Name
- We have
Sale
class with following properties -ProductId, Price
- The tables are loaded with product and sale collection.
- Click on Intersect 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 | |
---|---|
Product Id | Price |
1 | 1000 |
1 | 1000 |
2 | 1000 |
Products Sold :
Using LINQ Intersect to compare with Equality Comparer
So, equality for primitive data types with Intersect()
is easy and straight forward, but with objects by default it's going to work by
comparing object references. But in most cases we want to make comparison based on one or more properties in the object. To do that we need to start by creating
EqualityComparer<T>
class.
- Create a
ProductComparer
class that inherits fromEqualityComparer<Product>
class. - Override
Equals(Product 1, Product 2) method.
- Write the conditions to check equality and return true if both matches.
- Also override
GetHashCode()
method and return unique value for every single object.
Code Sample - LINQ Intersect Product Comparer
Code Sample - LINQ Intersect With Product Comparer
Demo - LINQ Intersect Clause with Comparer Demo
Let's try LINQ Intersect with Comparer
- We have
Product
class with following properties -Id, Name
- The tables are loaded with two product collection.
- Click on Except Button to view the result.
- Unlike previous demo, here we use
ProductComparer
to compare objects based on their property values. So they will be equal irrespective of reference. - Click on reset to try other combination
Id | Name |
---|---|
1 | Shirt |
2 | Shirt |
3 | Shirt |
4 | Shirt |
5 | Shirt |
6 | Shirt |
Id | Name |
---|---|
1 | Shirt |
2 | Shirt |
3 | Shirt |
4 | Shirt |
Common Product Id :
Using LINQ Intersect By to compare objects with Primitive Types
Starting .NET 6, Microsoft added IntersectBy()
which is similar to Intersect
in functionality but with an
simplification that we don't need to use a comparer class. We can use Key Expression
to find the common.
Code Sample - LINQ Intersect By Primitive Types
Demo - LINQ Intersect By Clause Demo
Let's try LINQ Intersect By with integer type
- Enter number and add it to sequence
- For demo purpose I have restricted sequence length to 3
- The Key Expression here is the Product ID. So whatever ID you enter in above sequence, IntersectBy() will compare and return the common Products from collection.
- For demo purpose I will be displaying only Product ID's
- Click on Intersect By Button to view the result
- Click on reset to try other combination
Id | Name |
---|---|
1 | Shirt |
2 | Shirt |
3 | Shirt |
4 | Shirt |
5 | Shirt |
6 | Shirt |
Common Product Ids :
Using LINQ Intersect By to compare objects
Previously, we saw a demo on how to find products that are sold. We can also perform the same function using IntersectBy()
. Unlike
Intersect()
, IntersectBy()
will return list of Product
instead of
product Id's.
Code Sample - LINQ Intersect By Objects
Demo - LINQ Intersect By Clause Demo
Let's try LINQ Intersect By with objects
- We have
Product
class with following properties -Id, Name
- We have
Sale
class with following properties -ProductId, Price
- The tables are loaded with product and sale collection.
- The Key Expression here is the Product ID. IntersectBy() will compare and return the common Products from collection.
- For demo purpose I will be displaying only Product ID's
- Click on Intersect By 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 | |
---|---|
Product Id | Price |
1 | 1000 |
1 | 1000 |
2 | 1000 |
Products Sold :
Summary
In this article we learn't how to check for common data between collections using Intersect
and IntersectBy
.
This can be used to find if item is between collection matches or not and also we can compare object item using Comparer. All these can be used with any
IEnumerable
or IQueryable
types.