Linq Joins in C#
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LINQ (Language Integrated Query) is a powerful technology that allows us to query data from different sources like collections, arrays, databases, XML files, and more. One of the essential features of LINQ is the ability to perform Joins between different data sources. In this lesson, we will discuss the different types of Joins in LINQ, including Inner Join, Left Join, Group Join, and more.
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Inner Join:
An Inner Join is the most common type of Join in LINQ. It returns only the matching records from both tables. The syntax for Inner Join in LINQ is as follows:
var result = from table1 in dataSource1 join table2 in dataSource2 on table1.column equals table2.column select new { table1.column, table2.column };
In this syntax, dataSource1
and dataSource2
are the two data sources that are to be joined, column
is the common field between the tables, and result
is the variable that holds the joined data.
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Left Join:
A Left Join returns all the records from the left table and only the matching records from the right table. The syntax for Left Join in LINQ is as follows:
var result = from table1 in dataSource1 join table2 in dataSource2 on table1.column equals table2.column into temp from t in temp.DefaultIfEmpty() select new { table1.column, t.column };
In this syntax, dataSource1
and dataSource2
are the two data sources that are to be joined, column
is the common field between the tables, and result
is the variable that holds the joined data.
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Group Join:
A Group Join returns a group of matching records from both tables. The syntax for Group Join in LINQ is as follows:
var result = from table1 in dataSource1 join table2 in dataSource2 on table1.column equals table2.column into temp select new { table1.column, temp };
In this syntax, dataSource1
and dataSource2
are the two data sources that are to be joined, column
is the common field between the tables, and result
is the variable that holds the joined data.
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Cross Join:
A Cross Join returns all possible combinations of the records from both tables. The syntax for Cross Join in LINQ is as follows:
var result = from table1 in dataSource1 from table2 in dataSource2 select new { table1.column, table2.column };
In this syntax, dataSource1
and dataSource2
are the two data sources that are to be joined, and result
is the variable that holds the joined data.
In conclusion, LINQ Joins are a powerful feature that allows us to combine data from different sources based on a common field. The different types of Joins in LINQ include Inner Join, Left Join, Group Join, and Cross Join. By understanding the syntax and usage of these Joins, we can write efficient and effective LINQ queries to retrieve and manipulate data from multiple sources.