Using ORDER BY

NCache provides you with the ability to sort the data according to the given criteria using ORDER BY clause. The ORDER BY keyword lets you sort the result set in ascending or descending order as specified.

Pre-Requisites

Indexing for searchable objects and their attributes need to be configured first as explained in Configuring Query Indexes in Administrator's Guide.
Include the following namespace in your application:
- Alachisoft.NCache.Web.Caching
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 example sorts the products from the cache with UnitPrice greater than 100 based on their UnitsInStock sorted in descending order using ExecuteReader.

try
{
    // Pre-condition: Cache is already connected
    // Items are already present in the cache

    // Specify the query with the specified criteria
    // Use the fully qualified name of your own custom class
    string query = "SELECT Alachisoft.NCache.Sample.Data.Product WHERE this.UnitPrice > ? ORDER BY this.UnitsInStock DESC";

    // Add the values in the hashtable for executing query
    // The query will get all the items with ProductID lesser than 100
    // and arrange them according to the UnitsInStock in descending order
    Hashtable values = new Hashtable();
    values.Add("UnitPrice", 100);

    // Execute query using ExecuteReader 
    ICacheReader reader = cache.ExecuteReader(query, values);

    // Check if result set is not empty
    if (reader.FieldCount > 0)
    {
        while (reader.Read())
        {
            // Get the value of the result set
            Product result = (Product)reader.GetValue(1);
            // reader.GetValue(0) = Cache key
            // reader.GetValue(1) = Product object
        }
    }
    else
    {
        // Null query result set retrieved
    }
}
catch (OperationFailedException ex)
{
    if (ex.Message.Contains("Incorrect query format"))
    {
        // Make sure that the query format is correct
    }
    else if (ex.Message.Contains("Index is not defined"))
    {
        // Make sure that index is defined using Query Indexes through NCache Manager
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentException, ArgumentNullException
}

Recommendation: 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 SQL Searching at:

GitHub
Shipped with NCache: %NCHOME%\samples\dotnet\ObjectQueryLanguage

Using ORDER BY

Pre-Requisites

Additional Resources

See Also