Linq outer join

The syntax of using the LINQ Left Outer Join to get all the elements from the collection and matching the element from the right collection. From the above syntax, we used into and DefaultfEmpty methods to implement the left outer join to get the elements from the " objEmp1 ", linq outer join, " objDept1 " collections. From the above example, we are getting the elements from " objEmp1 ", " objDept1 " collections by using left outer join in LINQ and here we specified the condition to check if there is a department for the employee or not. In case if the department not mapped, it will take " No Department " linq outer join the condition.

Please read the following three articles before proceeding to this article, as they all are required to understand the Left Outer Join. The Left Join or Left Outer Join is a Join in which each data from the first data source will be returned irrespective of whether it has any correlated data present in the second data source. In this case, the un-matching data will take a null value. For a better understanding, please look at the following diagram, which shows the graphical representation of the Left Outer Join. So, in simple words, we can say that the Left Outer Join will return all the matching data from both the data sources and all the non-matching data from the left data source.

Linq outer join

Posted by Kamil Pakula Mar 6, 0. Want to build great APIs? Or become even better at it? Check our Ultimate ASP. NET technologies. Bonus materials Security book, Docker book, and other bonus files are included in the Premium package! We often use just a single data source. But sometimes we need data from more than one source, be it a database, a file, or a C collection, to mention just a few. This is where joins come in handy. There are a couple of types of joins and we will take a closer look at them. In the most common scenario, we need data from one source that is somehow related to data in another source. We can use inner joins when we need to combine matching data coming from different sources. A typical scenario is when we have to handle missing data. We could, for example, set a default value for any missing piece of data in either source. Another use case is data analysis.

C Programming. With the method syntax, we have to use the GroupJoin method. Upgrade to Microsoft Edge to take advantage of the latest features, security linq outer join, and technical support.

This web site uses cookies. By using the site you accept the cookie policy. When you use the LINQ join clause in the query expression syntax to combine two sets of related information, you perform an inner join. This means that you provide an expression that determines for each item in the first sequence, the matching items in the second. Where there is a match, one item is added to the resultant sequence.

Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Microsoft makes no warranties, express or implied, with respect to the information provided here. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. The expected behavior is that of an inner join. The outerKeySelector and innerKeySelector functions are used to extract keys from outer and inner , respectively. These keys are compared for equality to match elements from each sequence. A pair of elements is stored for each element in inner that matches an element in outer.

Linq outer join

The Full Outer Join retrieves all the matching records from both the data sources involved in the join and all the non-matching records from both data sources. The Unmatching data in such cases will take the default value, i. To perform a full outer join using LINQ in C , you typically work with two collections and join them on a common key. So, first, create a class file with the name Employee. The following Employee class has 3 properties, i. Next, create another class file with the name Department.

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In the following example, the resulting objects are anonymous types that consist of the department name and the name of the teacher that leads the department. The corresponding elements from the second collection, which in this example are Student objects, are grouped into a collection. In our example, we created two methods that will be going to return the respective Employees and Addresses, which are going to be our data sources. Your email address will not be published. From the above example, we are getting the elements from " objEmp1 ", " objDept1 " collections by using left outer join in LINQ and here we specified the condition to check if there is a department for the employee or not. The following example matches Teacher objects with Deparment objects whose TeacherId matches that Teacher. We could, for example, set a default value for any missing piece of data in either source. EmployeeMasters from d in Context. Join Queryable. In the code snippet below, as you can see, the list of Employees is inner-joined with the list of Addresses based on the AddressId Property of the Employee object that matches the ID property of the Address object. So, modify the Main method of the Program class as follows to project the result to the EmployeeResult type. In this example, the list of Department objects is inner-joined to the list of Student objects based on a Department object's ID that matches the student's DepartmentID. Skip to content. Collaborate with us on GitHub. Instead of projecting the result to an anonymous type, we can also project the result to a named type with LINQ Method Syntax.

I think most C developers would agree that LINQ is an integral part of the experience of writing code with the language. LINQ provides a fluent, intuitive, and consistent way to query data sets. LINQ is available in two different flavors, the query syntax and the method syntax.

Data Mining. The left excluding join returns the non-matching data from the first source. In both cases, the non-matching data takes the null value or any default value that we provide. Compiler Design. The select clause in C defines how the resulting objects look. The category includes a name and the name of the major category that it belongs to. The full outer excluding join returns the non-matching data from both sources. This class has 3 properties, i. In this case, the un-matching data will take a null value. The into keyword is used to create a temporary grouping of results for each order, and the DefaultIfEmpty method is used to specify the left join behavior. Interview Questions. The DefaultIfEmpty method returns a collection containing a default value if the sequence of matching Address objects is empty for any Employee object, ensuring that each Employee object is represented in the result collection.