It is possible to set one Icon so, that it would be used on every window in current app. So that i set it once (not on every window by hand)..?
A good reference on the subject is here MSDN. States that you have an Icon for the Application (Desktop Icon), and one for each Window.
A WPF window always displays an icon. When one is not provided by setting Icon, WPF chooses an icon to display based on the following rules:
Use the assembly icon, if specified.
If the assembly icon is not specified, use the default Microsoft Windows icon.
Community Content Reference:
"A liitle tip : if you set the application icon and expect to see it on the window - it wont show up if running in debug from VS. Running externally or without attaching (ctrl + f5) the icon displays as expected."
Set the icon in the project properties on the "Application" tab in the "Resources" section. This icon will be the default icon for all windows in the application.