SPUserCollection Class

Represents a collection of SPUser objects.

Namespace:  Microsoft.SharePoint
Assembly:  Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Available in Sandboxed Solutions: Yes
Available in SharePoint Online

[ClientCallableTypeAttribute(Name = "UserCollection", ServerTypeId = "{e090781e-8899-4672-9b3d-a78f49fad19d}", 
	CollectionChildItemType = typeof(SPUser))]
public class SPUserCollection : SPMemberCollection

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.