Essential C# LINQ Queries  Suggest an edit

Basics

LINQ is largely beneficial for querying collections (or arrays).

For example, given the following sample data:

var classroom = new Classroom
{
    new Student { Name = "Alice", Grade = 97, HasSnack = true  },
    new Student { Name = "Bob",   Grade = 82, HasSnack = false },
    new Student { Name = "Jimmy", Grade = 71, HasSnack = true  },
    new Student { Name = "Greg",  Grade = 90, HasSnack = false },
    new Student { Name = "Joe",   Grade = 59, HasSnack = false }
}

We can “query” on this data using LINQ syntax. For example, to retrieve all students who have a snack today:

var studentsWithSnacks = from s in classroom.Students
                         where s.HasSnack
                         select s;

Or, to retrieve students with a grade of 90 or above, and only return their names, not the full Student object:

var topStudentNames = from s in classroom.Students
                      where s.Grade >= 90
                      select s.Name;

The LINQ feature is comprised of two syntaxes that perform the same functions, have nearly identical performance, but are written very differently. The syntax in the example above is called query syntax. The following example, however, illustrates method syntax. The same data will be returned as in the example above, but the way the query is written is different.

var topStudentNames = classroom.Students
                                   .Where(s => s.Grade >= 90)
                                   .Select(s => s.Name);

Table Of Contents
22 Enum
25 GUID
65 LINQ Queries
107 Stream
108 Timers
  ↑ ↓ to navigate     ↵ to select     Esc to close