/// <summary>
/// Removes an object from the backing store.
/// </summary>
/// <param name="id">The StateServer identifier of the object to delete from the backing store.</param>
public void Erase(CachedObjectId id)
{
// Write-behind will call this Erase implementation if an object is removed from the named cache.
// If you want the object removed from the DB in that situation, this is the place to do it:
try
{
if (Configuration.USE_DATABASE)
{
using (SqlConnection conn = new SqlConnection(Configuration.CONNECTION_STRING))
{
conn.Open();
SqlCommand cmd = new SqlCommand("Delete", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new SqlParameter("@ID", Convert.ToInt32(id.GetStringKey())));
// Execute the command
cmd.ExecuteNonQuery();
}
}
Logger.WriteMessage(TraceEventType.Information, 12, $"The Erase method is called for object {id.GetStringKey()}");
}
catch (Exception ex)
{
Logger.WriteMessage(TraceEventType.Error, 13, $"Exception occurred in the Erase method: {ex.ToString()}");
}
}
/// <summary>
/// Loads an object from the backing store. Return null if there is no value in the backing store for the specified id.
/// </summary>
/// <param name="id">The identifier of the object to retrieve from the backing store.</param>
/// <returns>The object from the backing store that is to be loaded into ScaleOut StateServer, or null if the object was not found.</returns>
public object Load(CachedObjectId id)
{
// This Load method won't ever be invoked because we aren't performing Refresh-Ahead in this sample.
// For read-through and/or refresh-ahead approaches, this method should:
// 1. Obtain data from the database for specified object's Id.
// 2. Create and return object back to application.
return(null);
}
/// <summary>
/// Provides a policy object to be used when a Load(CachedObjectId) operation inserts an object into the named cache.
/// If the method returns null then the named cache's DefaultCreatePolicy will be used.
/// </summary>
/// <param name="id">The identifier of the object being loaded into the cache.</param>
/// <returns>
/// The CreatePolicy to be used when inserting the specified object into the cache,
/// or null if the named cache's DefaultCreatePolicy is to be used.
/// </returns>
public CreatePolicy GetCreatePolicy(CachedObjectId id)
{
// This GetCreatePolicy method is only called when we're handling read-through events.
// If we did need to implement it, however, returning null causes read-through to use
// the NamedCache's default create policy when adding an object to the cache.
return(null);
// Here is how you can create and return CreatePolicy class instance with object specific characteristics:
//
// var policy = new CreatePolicy();
// policy.BackingStoreMode = BackingStoreAsyncPolicy.WriteBehind;
// policy.BackingStoreInterval = TimeSpan.FromSeconds(30);
// policy.Timeout = new TimeSpan(0, 5, 0); // 5 minutes
// return policy;
}
// Sample uses one table and two stored procedures defined in the WriteBehindEventHandler_DatabaseObjects.sql file.
// The USE_DATABASE and CONNECTION_STRING properties are defined in the Configuration class, that is part of
// the Common project and can be overwritten by corresponding settings in the app.config file of the WriteBehindEventHandler service.
#region IBackingStore Members
/// <summary>
/// Persists an object to the backing store.
/// </summary>
/// <param name="id">The StateServer identifier of the object to persist.</param>
/// <param name="value">The cached object to be written to the backing store.</param>
public void Store(CachedObjectId id, object value)
{
// The value parameter is the object that's been stored in the cache and needs to be written to the DB.
// In this example, the incoming value will be of the SampleObject type.
try
{
if (Configuration.USE_DATABASE)
{
SampleObject saObj = value as SampleObject;
if (saObj != null)
{
using (SqlConnection conn = new SqlConnection(Configuration.CONNECTION_STRING))
{
conn.Open();
SqlCommand cmd = new SqlCommand("AddOrUpdate", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new SqlParameter("@ID", Convert.ToInt32(id.GetStringKey())));
cmd.Parameters.Add(new SqlParameter("@IntVal", saObj.IntVal));
cmd.Parameters.Add(new SqlParameter("@DoubleVal", saObj.DoubleVal));
cmd.Parameters.Add(new SqlParameter("@StringVal", saObj.StringVal));
// Execute the command
cmd.ExecuteNonQuery();
}
}
}
Logger.WriteMessage(TraceEventType.Information, 10, $"The Store method is called for object {id.ToString()} with value {value.ToString()}");
}
catch (Exception ex)
{
Logger.WriteMessage(TraceEventType.Error, 11, $"Exception occurred in the Store method: {ex.ToString()}");
}
}