Using IN Operator

In order to search the cache using SQL like query format using IN Operator, you can specify multiple attribute values after the IN keyword which means that ExecuteReader() will search the cache for all the attributes provided after the IN keyword.

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 retrieves all the products from the cache which belong to either Beverages, Produce or Seafood category 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.Category IN (?,?,?)";

  // Create a new array list and add categories for the query in it
  ArrayList categoryList = new ArrayList();
  categoryList.Add("Beverages");
  categoryList.Add("Produce");
  categoryList.Add("Seafood");

  // Add the values in the hashtable for executing query
  Hashtable values = new Hashtable();
  values.Add("Category", categoryList);

  // 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 IN Operator

Pre-Requisites

Additional Resources

See Also