public virtual void StartAdvise(string item, int format, bool hot, bool acknowledge, int timeout, object adviseState)
{
if (IsDisposed)
{
throw new ObjectDisposedException(this.GetType().ToString());
}
if (!IsConnected)
{
throw new InvalidOperationException(Resources.NotConnectedMessage);
}
if (item == null)
{
throw new ArgumentNullException("item");
}
if (item.Length > Ddeml.MAX_STRING_SIZE)
{
throw new ArgumentException(Resources.StringParameterInvalidMessage, "item");
}
if (timeout <= 0)
{
throw new ArgumentException(Resources.TimeoutParameterInvalidMessage, "timeout");
}
if (_AdviseLoopTable.ContainsKey(item))
{
string message = Resources.AlreadyBeingAdvisedMessage;
message = message.Replace("${service}", _Service);
message = message.Replace("${topic}", _Topic);
message = message.Replace("${item}", item);
throw new InvalidOperationException(message);
}
// Create a AdviseLoop object to associate with this advise loop and add it to the advise loop table.
// The object is added to the advise loop table first because an advisory could come in synchronously during the call
// DdeClientTransaction. The assumption is that the advise loop will be initiated successfully. If it is not then the object must
// be removed from the advise loop table prior to leaving this method.
AdviseLoop adviseLoop = new AdviseLoop(this);
adviseLoop.Item = item;
adviseLoop.Format = format;
adviseLoop.State = adviseState;
_AdviseLoopTable.Add(item, adviseLoop);
// Determine whether the client should acknowledge an advisory before the server posts another.
bool ack = acknowledge;
// Create a string handle for the item name.
IntPtr itemHandle = Ddeml.DdeCreateStringHandle(_InstanceId, item, Ddeml.CP_WINANSI);
// Initiate an advise loop.
int type = Ddeml.XTYP_ADVSTART;
type = !hot ? type | Ddeml.XTYPF_NODATA : type;
type = ack ? type | Ddeml.XTYPF_ACKREQ : type;
int returnFlags = 0;
IntPtr result = Ddeml.DdeClientTransaction(
IntPtr.Zero,
0,
_ConversationHandle,
itemHandle,
format,
type,
timeout,
ref returnFlags);
// Free the string handle created earlier.
Ddeml.DdeFreeStringHandle(_InstanceId, itemHandle);
// If the result is null then the server did not initate the advise loop.
if (result == IntPtr.Zero)
{
// Remove the AdviseLoop object created earlier from the advise loop table. It is no longer valid.
_AdviseLoopTable.Remove(item);
int error = Ddeml.DdeGetLastError(_InstanceId);
string message = Resources.StartAdviseFailedMessage;
message = message.Replace("${service}", _Service);
message = message.Replace("${topic}", _Topic);
message = message.Replace("${item}", item);
throw new DdemlException(message, error);
}
}
protected override IntPtr ProcessCallback(
int uType, int uFmt, IntPtr hConv, IntPtr hsz1, IntPtr hsz2, IntPtr hData, IntPtr dwData1, IntPtr dwData2)
{
// If the data handle is null then the server did not initiate the advise loop.
if (hData == IntPtr.Zero)
{
string message = Resources.StartAdviseFailedMessage;
message = message.Replace("${service}", this.Client._Service);
message = message.Replace("${topic}", this.Client._Topic);
message = message.Replace("${item}", _Item);
this.ExceptionObject = new DdemlException(message);
}
else
{
// Create a AdviseLoop object to associate with this advise loop and add it to the owner's advise loop table.
AdviseLoop adviseLoop = new AdviseLoop(this.Client);
adviseLoop.Item = _Item;
adviseLoop.Format = _Format;
adviseLoop.State = _State;
this.Client._AdviseLoopTable.Add(_Item, adviseLoop);
}
// Return zero to indicate that there are no problems.
return IntPtr.Zero;
}