Using LIKE Operator

NCache allows you to use the LIKE Operator in the query to search for a specific pattern in a column.

The two wildcards used with the LIKE operator are:

*: Used as a substitute for zero or more characters in the string.
?: Used as a substitute for a single character in the string.

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 searches the cache and retrieves all the products that have their ProductName starting with the letter Ch 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.ProductName LIKE ?";

  // Add the values in the hashtable for executing query
  // The query will get all the items with productName starting  with "Ch"
  // For example Chai as well as Chocolate
  Hashtable values = new Hashtable();
  values.Add("ProductName", "Ch*");

  // 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 LIKE Operator

Pre-Requisites

Additional Resources

See Also