/// <summary>
/// Sends an asynchronous request to read the attributes of an item.
/// </summary>
/// <param name="startTime">The beginning of the history period to read.</param>
/// <param name="endTime">The end of the history period to be read.</param>
/// <param name="item">The item to read (must include the server handle).</param>
/// <param name="attributeIDs">The attributes to read.</param>
/// <param name="requestHandle">An identifier for the request assigned by the caller.</param>
/// <param name="callback">A delegate used to receive notifications when the request completes.</param>
/// <param name="request">An object that contains the state of the request (used to cancel the request).</param>
/// <returns>A set of results containing any errors encountered when the server validated the attribute ids.</returns>
public ResultCollection ReadAttributes(
Time startTime,
Time endTime,
ItemIdentifier item,
int[] attributeIDs,
object requestHandle,
ReadAttributesEventHandler callback,
out IRequest request)
{
if (m_server == null)
{
throw new NotConnectedException();
}
ResultCollection results = ((IServer)m_server).ReadAttributes(
startTime,
endTime,
item,
attributeIDs,
requestHandle,
callback,
out request);
return(results);
}
/// <summary>
/// Invokes callback for a read attributes request.
/// </summary>
private bool InvokeCallback(ReadAttributesEventHandler callback, object results)
{
// check for valid result type.
if (!typeof(ItemAttributeCollection).IsInstanceOfType(results))
{
return(false);
}
ItemAttributeCollection values = (ItemAttributeCollection)results;
// update item handles and actual times.
UpdateResults(new ItemAttributeCollection[] { values });
try
{
callback(this, values);
}
catch
{
// ignore exceptions in the callbacks.
}
// request always completes
return(true);
}
private bool InvokeCallback(ReadAttributesEventHandler callback, object results)
{
if (!typeof(ItemAttributeCollection).IsInstanceOfType(results))
{
return(false);
}
ItemAttributeCollection attributes = (ItemAttributeCollection)results;
this.UpdateResults(new ItemAttributeCollection[] { attributes });
try
{
callback(this, attributes);
}
catch
{
}
return(true);
}
/// <summary>
/// Starts an asynchronous read attributes at specific times request for an item.
/// </summary>
public ResultCollection ReadAttributes(
ItemIdentifier item,
int[] attributeIDs,
object requestHandle,
ReadAttributesEventHandler callback,
out IRequest request)
{
ResultCollection results = m_server.ReadAttributes(
StartTime,
EndTime,
item,
attributeIDs,
requestHandle,
callback,
out request);
return(results);
}
public ResultCollection ReadAttributes(ItemIdentifier item, int[] attributeIDs, object requestHandle, ReadAttributesEventHandler callback, out IRequest request)
{
return(this.m_server.ReadAttributes(this.StartTime, this.EndTime, item, attributeIDs, requestHandle, callback, out request));
}
