The RedisCollection provides a fluent interface for querying objects stored in redis. This means that if you store an object in Redis with the Redis OM library, and you have Redis Stack running, you can query objects stored in Redis with ease using the LINQ syntax you're used to.
Let's start off by defining a model that we will be using for querying, we will use a Employee Class which will have some basic stuff we may want to query in it
[Document]
public class Employee
{
[Indexed]
public string Name { get; set; }
[Indexed(Aggregatable = true)]
public int Age { get; set; }
[Indexed(Aggregatable = true)]
public double Sales { get; set; }
[Searchable(Aggregatable = true)]
public string Department { get; set; }
}Now we will initialize a RedisConnectionProvider, and grab a handle to a RedisCollection for Employee
static async Task Main(string[] args)
{
var provider = new RedisConnectionProvider("redis://localhost:6379");
var connection = provider.Connection;
var employees = prover.RedisCollection<Employee>();
await connection.CreateIndexAsync(typeof(Employee));
}Next we'll create the index, so next in our Main method, let's take our type and condense it into an index
Next we'll seed a few piece of data in our database to play around with:
var e1 = new Employee {Name = "Bob", Age = 35, Sales = 100000, Department = "EMEA Sales"};
var e2 = new Employee {Name = "Alice", Age = 52, Sales = 300000, Department = "Partner Sales"};
var e3 = new Employee {Name = "Marcus", Age = 42, Sales = 250000, Department = "NA Sales"};
var e4 = new Employee {Name = "Susan", Age = 27, Sales = 200000, Department = "EMEA Sales"};
var e5 = new Employee {Name = "John", Age = 38, Sales = 275000, Department = "APAC Sales"};
var e6 = new Employee {Name = "Theresa", Age = 30, Department = "EMEA Ops"};
var insertTasks = new []
{
employees.InsertAsync(e1),
employees.InsertAsync(e2),
employees.InsertAsync(e3),
employees.InsertAsync(e4),
employees.InsertAsync(e5)
employees.InsertAsync(e6)
};
await Task.WhenAll(insertTasks);With these data inserted into our database, we can now go ahead and begin querying. Let's start out by trying to query people by name. We can search for all employees named Susan with a simple Where predicate:
var susans = employees.Where(x => x.Name == "Susan");
await foreach (var susan in susans)
{
Console.WriteLine($"Susan is {susan.Age} years old and works in the {susan.Department} department ");
}The Where Predicates also support and/or operators, e.g. to find all employees named Alice or Bob you can use:
var AliceOrBobs = employees.Where(x => x.Name == "Alice" || x.Name == "Bob");
await foreach (var employee in AliceOrBobs)
{
Console.WriteLine($"{employee.Name} is {employee.Age} years old and works in the {employee.Department} Department");
}When you are querying larger Documents in Redis, you may not want to have to drag back the entire object over the network, in that case you can limit the results to only what you want using a Select predicate. E.g. if you only wanted to find out the ages of employees, all you would need to do is select the age of employees:
var employeeAges = employees.Select(x => x.Age);
await foreach (var age in employeeAges)
{
Console.WriteLine($"age: {age}");
}Or if you want to select more than one field you can create a new anonymous object:
var employeeAges = employees.Select(x => new {x.Name, x.Age});
await foreach (var e in employeeAges)
{
Console.WriteLine($"{e.Name} is age: {e.Age} years old");
}You can limit the size of your result (in the number of objects returned) with Skip & Take predicates. Skip will skip over the specified number of records, and Take will take only the number of records provided (at most);
var people = employees.Skip(1).Take(2);
await foreach (var e in people)
{
Console.WriteLine($"{e.Name} is age: {e.Age} years old");
}There are two types of attributes that can decorate strings, Indexed, which we've gone over and Searchable which we've yet to discuss. The Searchable attribute considers equality slightly differently than Indexed, it operates off a full-text search. In expressions involving Searchable fields, equality—==— means a match. A match in the context of a searchable field is not necessarily a full exact match but rather that the string contains the search text. Let's look at some examples.
So we have a Department string which is marked as Searchable in our Employee class. Notice how we've named our departments. They contain a region and a department type. If we wanted only to find all employee's in Sales we could do so with:
var salesPeople = employees.Where(x => x.Department == "Sales");
await foreach (var employee in salesPeople)
{
Console.WriteLine($"{employee.Name} is in the {employee.Department} department");
}This will produce:
Bob is in the EMEA Sales department
Alice is in the Partner Sales department
Marcus is in the NA Sales department
Susan is in the EMEA Sales department
John is in the APAC Sales departmentBecause they are all folks in departments called sales
If you wanted to search for everyone in a department in EMEA you could search with:
var emeaFolks = employees.Where(x => x.Department == "EMEA");
await foreach (var employee in emeaFolks)
{
Console.WriteLine($"{employee.Name} is in the {employee.Department} department");
}Which of course would produce:
Bob is in the EMEA Sales department
Susan is in the EMEA Sales department
Theresa is in the EMEA Ops departmentIf a Searchable or Indexed field is marked as Sortable, or Aggregatable, you can order by that field using OrderBy predicates.
var employeesBySales = employees.OrderBy(x=>x.Name);
var employeesBySalesDescending = employees.OrderByDescending(x=>x.Name);