Gets or sets the pre-filtering GUID for an externally matched alert.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
The MatchId property throws an SPException in the following situations:
If the alert applies to list or item.
If the AlertType property does not contain Custom.
If set prior to setting the AlertType property.
If changed after the Update method is called.
This property is required if the AlertType property contains Custom. If an existing list GUID is specified, the alert matches all events on the list, but it does not appear in alert management UI.