SPSite.ReadOnly Property
Gets or sets a Boolean value that specifies whether the site collection is read-only, locked, and unavailable for write access.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Available in Sandboxed Solutions: Yes
Available in SharePoint Online
Property Value
Type: System.Booleantrue if the site collection is read-only, locked, and unavailable for write access; otherwise, false.
Setting ReadOnly to true or false also sets WriteLocked to the same value.
ReadOnly returns true whenever the IsReadOnly property of the parent SPDatabase object is true.