What does GroupBy do in LINQ?
Grouping is a very powerful feature provided by LINQ that transforms a collection in groups where each group has a key associated with it. Note: GroupBy performs a deferred execution which means the query is only executed when the records are processed using a foreach loop.
How use LINQ Group data in C#?
The Linq GroupBy in C# belongs to the Grouping Operators category and exactly does the same thing as the Group By clause does in SQL Query. This method takes a flat sequence of elements and then organizes the elements into groups (i.e. IGrouping) based on a given key.
What is GroupBy C#?
GroupBy() Method in C# The GroupBy() is an extension method that returns a group of elements from the given collection based on some key value. arr. GroupBy(b => chkSmaller(b)); The above chkSmaller() finds the elements smaller than 50.
What is where in LINQ?
The Where operator (Linq extension method) filters the collection based on a given criteria expression and returns a new collection. The criteria can be specified as lambda expression or Func delegate type. The Where extension method has following two overloads.
How use contains in LINQ query?
LINQ Contains operator is used to check whether an element is available in sequence (collection) or not. Contains operator comes under Quantifier Operators category in LINQ Query Operators. Below is the syntax of Contains operator. public static bool Contains( this IEnumerable source, TSource value);
How use contains in LINQ?
All, Any & Contains are quantifier operators in LINQ. All checks if all the elements in a sequence satisfies the specified condition. Any check if any of the elements in a sequence satisfies the specified condition. Contains operator checks whether specified element exists in the collection or not.
Why we use IQueryable in LINQ?
IQueryable is suitable for querying data from out-memory (like remote database, service) collections. While querying data from a database, IQueryable executes a “select query” on server-side with all filters. IQueryable is beneficial for LINQ to SQL queries.
What is the LINQ equivalent to the SQL IN operator?
LINQ does not have an operator directly equivalent to IN or NOT IN, but it offers a Contains operator that you can use to write the code in Listing 5-27. Pay attention to the not operator (!) applied to the where predicate, which negates the Contains condition that follows.
How to dynamically build up a query in LINQ?
– var result = from T1 in liCust – join T2 in liOrder – on T1.OrderId equals T2.OrderId – select new {T1.OrderId,T1.CustomerName,T1.CustomerID, – T2.ProductCost,T2.ProductName};
Why is LINQ important for querying?
Composability. You might have noticed another more subtle (but important) benefit of the LINQ approach.
How to join two LINQ queries?
var result = eventDocuments.Join (events, doc => new { doc.ID1, doc.ID2 }, ev => new { cross.DocID1, cross.DocID2}, (doc, ev) => new { EventDocument = doc, Event = ev }); You can simply query both sets with SelectMany. In query syntax this would look like: You don’t need to use one query to filter your results.
How to use LINQ groupby?
By a single property.