As stated in the Overview article, RadShortcuts are assigned at RadItem level. That said, you can't assign a shortcut directly to a RadControl (RadButton for example). Instead, you should assign the shortcut to the main element of a RadControl. For example, considering our buttons, you can assign shortcuts to them as it is shown below:
Copy[C#]
this.radButton1.ButtonElement.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.B));
this.radRadioButton1.ButtonElement.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.R));
this.radSplitButton1.DropDownButtonElement.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.S));
this.radToggleButton1.ButtonElement.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.T));
Copy[VB.NET]
Me.RadButton1.ButtonElement.Shortcuts.Add(New RadShortcut(Keys.Control, Keys.B))
Me.RadRadioButton1.ButtonElement.Shortcuts.Add(New RadShortcut(Keys.Control, Keys.R))
Me.RadSplitButton1.DropDownButtonElement.Shortcuts.Add(New RadShortcut(Keys.Control, Keys.S))
Me.RadToggleButton1.ButtonElement.Shortcuts.Add(New RadShortcut(Keys.Control, Keys.T))