Does NCache support server-side LINQ filtering?

Yes, NCache executes LINQ query on the server-side, giving only the filtered result set to the client, which reduces network traffic.

Which LINQ operators are supported by NCache?

NCache supports Projection operators such as Select, Restriction operators such as Where, comparison operators such as == and !=, logical operators such as && and ||, aggregation operators such as Sum, Count, Average, Max, and Min, and wildcard operations such as StartsWith, EndsWith, Contains, and Equals.

Use LINQ Queries for Objects

NCache integrates with the Language Integrated Query (LINQ) provider to enable developers to search distributed cached data using standard .NET LINQ expressions. It is integrated using the NCacheQuery class, which implements the IQueryable interface provided by the .NET framework. This allows for seamless object querying within a distributed cache using familiar LINQ syntax.

To use LINQ with NCache, initialize the cache and create an NCacheQuery<T> instance for the type you want to query. Existing LINQ query expressions can then be executed against this queryable object.

LINQ Queries: Querying Objects through NCacheQuery class

You can use any of the following supported LINQ operators to retrieve NCache objects using NCacheQuery:

Projection Operators: Transform data using operators like Select.
Restriction Operators: Filter data using criteria like Where.
Basic Query Operators: Compare values using operators such as ==, !=, <, >, <=, and >=.
Logical Operators: Combine multiple criteria using && (AND) and || (OR).
Aggregation Operators: Perform calculations like Sum, Count, Average, Max, and Min on the server-side.
Wildcard Query Operators: Perform string matching using StartsWith, EndsWith, Contains, and Equals.

Prerequisites to Use LINQ Queries

Before using LINQ queries, ensure that following prerequisites are fulfilled:

.NET

Install the following NuGet packages in your .NET client application:
- Enterprise: Linq.NCache
Include the following namespaces in your application:
Indexing for searchable objects and their attributes needs to be configured first as explained in our section on Dynamic Indexing and Configuring Query Indexes in the Administrator's Guide.
The cache must be running.
For API details, refer to: NCacheQuery.

LINQ Operations

The following code uses the NCacheQuery class to demonstrate several operators we've discussed and illustrate how to use NCache with LINQ.

Using Query Expression

.NET

try
{
  // Precondition: Cache is already connected
  // Create custom class LINQ object
  IQueryable<Product> products = new NCacheQuery<Product>(cache);

  // LINQ query to search cache
  IQueryable<Product> result = from prod in products where (prod.Category == "Beverages" || prod.Category == "Dairy") && prod.UnitsInStock > 10 select prod;

  if (result != null)
  {
      foreach (Product product in result)
      {
          Console.WriteLine($"Product '{product.ProductName}' in Category '{product.Category}' has stock of '{product.UnitsInStock}' units");
      }
  }
  else
  {
      Console.WriteLine($"No product found");
  }
}
catch (OperationFailedException ex)
{
    //NCache specific exception
    // Exception can occur due to:
    // Connection Failures
    // Operation Timeout
    // Operation performed during state transfer
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Using Lambda Expression

.NET

// Lambda expression for same query
IQueryable<Product> result = products.Select(prod => prod).Where(prod => ((prod.Category == "Beverages" || prod.Category == "Dairy") && prod.UnitsInStock > 10));

Note

To ensure the operation is fail-safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Additional Resources

NCache provides sample application for NCache LINQ on GitHub.