- The structure of an inner join is lackluster.…In my example some customers have multiple…distributors they can pick from…which adds a separate entry for each match.…It would be better to receive the results…in a hierarchical fashion,…where for each customer a list of distributors is returned.…To accomplish that I'll use a GroupJoin.…When executing a GroupJoin the elements…of the left sequence are associated…with one or more matching elements…in the right sequence.…This is also called an"Outer Join"…because the resulting sequence…will include the elements in the left sequence…that are outside of the overlapping areas.…
GroupJoin provides a similar functionality as Join,…but instead of returning a flat structure…it can return a structured result…grouped by each outer element in the resource sequence.…If no matches are found, it will produce…an empty array for that item…as seen here with customer Brock.…To accomplish a GroupJoin I'll add…an into expression to the join clause.…I'll cover the details about the into keyword…
Author
Released
11/30/2015In LINQ with C# Essential Training, engineer Olivia Chiu introduces techniques for querying, updating, and transforming data with LINQ. She covers standard queries—such as finding overlaps in two datasets and creating hierarchies—as well as complex chained queries. She also shows how to group and join LINQ queries with lambda expressions, and use LINQ to query SQL databases and XML documents. Last but not least, Olivia provides tips for optimizing the performance of your queries.
- Creating and executing a LINQ query
- Returning results
- Changing the data source type
- Performing standard queries
- Working with lambda expressions
- Chaining and complex queries
- Querying SQL and XML
- Performing tree queries
- Using sequences, elements, and scalars
- Allocating memory
Skill Level Intermediate
Duration
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Introduction
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Welcome51s
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Use the exercise files1m 6s
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1. Introduction to LINQ
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Common use cases1m 45s
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2. Basic LINQ Queries
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Select a data source3m 6s
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Create a query1m 33s
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Execute a query1m 56s
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3. Data Transformation
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Return results as a new type1m 39s
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4. Type Relationships
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5. Standard Queries
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Parse basic groups4m 30s
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Create hierachy in a dataset3m 50s
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6. Lambda Expressions
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Lambda expressions3m 25s
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Index and distinct operators2m 22s
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Take and skip operators2m 47s
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7. Complex Queries
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Chaining2m 9s
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Use the into keyword3m 45s
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Use the let keyword3m 4s
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8. LINQ to SQL
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Database setup3m 58s
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Database query1m 48s
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Database updates2m 56s
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9. LINQ to XML
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Tree creation4m 10s
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Tree queries1m 43s
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10. Other Operators
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11. Performance
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Memory allocation1m 54s
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Best practices1m 40s
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Conclusion
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Next steps44s
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Video: Create hierachy in a dataset