Using Basic Query Operators

NCache supports multiple basic query operators with LINQ.

Pre-Requisites

For flawless program delivery, ensure the following:

• Include the following namespaces in your application:
  • AlalchiSoft.NCache.Web.Caching
  • Alachisoft.NCache.Linq (located at %NCHOME%\integrations\LINQToNCache)
• Indexing for searchable objects and their attributes need to be configured first as explained in Configuring Query Indexes in Administrator's Guide.
• The application must be connected to cache before performing the operation.
• Cache must be running.
• Make sure that the data being added is serializable.
• To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

The following code uses the NCacheQuery class with two of the basic query operators '>' and '=='. It is assumed the cache contains Product objects.

Basic Query Operator '>':

A Product class LINQ object is created which is used to query products which have ProductID > 1001.

Using Simple LINQ Query Expression:

try
{
    // Precondition: Cache is already connected 

    // Create custom class LINQ object 
    IQueryable<Product> products = new NCacheQuery<Product>(cache);

    // LINQ query to search cache
    var result = from prod in products
                 where prod.ProductID > 1001
                 select prod;              

    if (result != null)
    {
        foreach (Product product in result)
        {
            // Perform operations
        }
    }
    else
    {
        // No result in the cache related to query
    }
}
catch (OperationFailedException ex)
{
    //NCache specific exception
    if (ex.Message.Contains("Index is not defined."))
    {
        // Index is not defined for the object queried.
        // Index all objects using NCache Manager or Config files.
    }
    else
    {
        //Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Using Lambda Expression:

try
{
    // Precondition: Cache is already connected 

    // Create custom class LINQ object 
    IQueryable<Product> products = new NCacheQuery<Product>(cache);

    // Lambda expression for same query
    var result = products.Select(prod => prod).Where(prod => prod.ProductID > 1001);

    if (result != null)
    {
        foreach (Product product in result)
        {
            // Perform operations
        }
    }
    else
    {
        // No result in the cache related to query
    }
}
catch (OperationFailedException ex)
{
    //NCache specific exception
    if (ex.Message.Contains("Index is not defined."))
    {
        // Index is not defined for the object queried.
        // Index all objects using NCache Manager or Config files.
    }
    else
    {
        //Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Basic Query Operator '==':

A Product class LINQ object is created which is used to query product which has a ProductID = 1001.

Using Simple LINQ Query Expression:

try
{
    // Precondition: Cache is already connected 

    // Create custom class LINQ object 
    IQueryable<Product> products = new NCacheQuery<Product>(cache);

    // LINQ query to search cache
    var result = from prod in products
                 where prod.ProductID == 1001
                 select prod;

    if (result != null)
    {
        foreach (Product product in result)
        {
            // Perform operations
        }
    }
    else
    {
        // No result in the cache related to query
    }
}
catch (OperationFailedException ex)
{
    //NCache specific exception
    if (ex.Message.Contains("Index is not defined."))
    {
        // Index is not defined for the object queried.
        // Index all objects using NCache Manager or Config files.
    }
    else
    {
        //Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Using Lambda Expression:

try
{
    // Precondition: Cache is already connected 

    // Create custom class LINQ object 
    IQueryable<Product> products = new NCacheQuery<Product>(cache);

    // Lambda expression for same query
    var result = products.Select(prod => prod).Where(prod => prod.ProductID == 1001);

    if (result != null)
        {
        foreach (Product product in result)
            {
                // Perform operations
            }
        }
    else
        {
            // No result in the cache related to query
        }
}
catch (OperationFailedException ex)
{
    //NCache specific exception
    if (ex.Message.Contains("Index is not defined."))
    {
        // Index is not defined for the object queried.
        // Index all objects using NCache Manager or Config files.
    }
    else
    {
        //Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Additional Resources

NCache provides sample application for using LINQ with NCache at:

• GitHub
• Shipped with NCache: %NCHOME%\samples\dotnet\NCacheLINQ

See Also

Search Objects with LINQ Query
Using Logical Operators
Using Aggregate Operators
Using Wildcard Operators