Can't use WpfAnimatedGif nuget package [duplicate]

I'm trying to make a WPF project that use nuget package of "WpfAnimatedGif" (https://github.com/XamlAnimatedGif/WpfAnimatedGif) in order to make a window background gif.But for some reason, i can't use this package after i install it. I try to use namespaces of the package, for example:

<Image gif:ImageBehavior.AnimatedSource="Resources\animated.gif"       gif:ImageBehavior.AutoStart="True"       gif:ImageBehavior.RepeatBehavior="1"/>

but the visual studio show erros like:"The namespace prefix "gif" is not defined."What can i do to solve this problem?thank you.

This is the XAML code:

<Window x:Class="TriviaGame.MainWindow"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    xmlns:local="clr-namespace:TriviaGame"    mc:Ignorable="d"    Title="MainWindow" Height="450" Width="800"><Grid><Image gif:ImageBehavior.AnimatedSource="Resources\animated.gif"       gif:ImageBehavior.AutoStart="True"       gif:ImageBehavior.RepeatBehavior="1"/></Grid>