ScriptManager.AsyncPostBackTimeout Property
.NET Framework 4.5
Gets or sets a value that indicates the time, in seconds, before asynchronous postbacks time out if no response is received.
Namespace: System.Web.UI
Assembly: System.Web.Extensions (in System.Web.Extensions.dll)
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.