【WPF】 .ico ファイルを Window のアイコンに設定する方法 ref: http://qiita.com/items/a672e945103d7dda284b

MainWindow.xaml

<Window x:Class="DiffFileSaver.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
        xmlns:l="http://schemas.livet-mvvm.net/2011/wpf"
        xmlns:v="clr-namespace:DiffFileSaver.Views"
        xmlns:vm="clr-namespace:DiffFileSaver.ViewModels"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        xmlns:scg="clr-namespace:System.Collections.Generic;assembly=mscorlib"
        Title="DiffFileSaver"
        Height="318.182"
        Width="525"
        Icon="/DiffFileSaver;component/Resources/unWatching.ico">

        <!-- 省略 -->

</Window>

MainWindow.xaml.cs

this.Icon = BitmapFrame.Create(new Uri("pack://application:,,,/Resources/unWatching.ico", UriKind.RelativeOrAbsolute));