elcapitanAndres, My code is XML not C#...Sorry for the confusion, I guess i'm lost on what you are trying to do. Originally you posted XML so I thought thats where you were working and wanted to stay. Why do it in C# when you can handle this in XML. You just want to create a hyperlink and when this link is clicked it takes the enduser to a website or image that is stored on your server? I'm binding to a fabricated field named "HyperLinkIDField" if you have a field with your link data just place that field there. I inserted my code into yours, it assumes that you have a field in your layer that has the link with the address (HyperLinkIDField) and then just binds that. Your code in RED - Mine in BLUE:
<esri:GraphicsLayer ID="Landmarks">
<esri:GraphicsLayer.MapTip>
<Border esri:GraphicsLayer.MapTipHideDelay="00:00:02" BorderBrush="DarkGray" CornerRadius="13" BorderThickness="1" Margin="0,0,15,15" Loaded="MapTipLoaded">
<Border.Effect>
<DropShadowEffect ShadowDepth="10" BlurRadius="14" Direction="300" />
</Border.Effect>
<Border CornerRadius="10" Background="#DDFFEEEE" BorderThickness="4" BorderBrush="#77FF0000" Name="MapTipBorder">
<StackPanel Orientation="Vertical" HorizontalAlignment="Center" Margin="10">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Path=[Event]}" HorizontalAlignment="Left" VerticalAlignment="Center" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="User: " FontWeight="Bold" Foreground="#FF0F274E" FontSize="10" VerticalAlignment="Center"/>
<TextBlock Text="{Binding Path=[User]}" HorizontalAlignment="Left" VerticalAlignment="Center" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Date: " FontWeight="Bold" Foreground="#FF0F274E" FontSize="10" VerticalAlignment="Center" />
<TextBlock Text="{Binding Path=[Date]}" HorizontalAlignment="Left" VerticalAlignment="Center" />
</StackPanel>
<StackPanel Orientation="Horizontal" Name="MapTipSPImages" >
<TextBlock Name="HyperlinkString" Visibility="Collapsed" Text="{Binding [HyperLinkIDField]}" HorizontalAlignment="Left" VerticalAlignment="Center" />
<HyperlinkButton TargetName="_blank" Content="Click Me I'm a HyperLink" HorizontalAlignment="Center" Foreground="RED" NavigateUri="{Binding Text, ElementName=HyperLinkString, Mode=OneWay}"/>
</StackPanel>
</StackPanel>
</Border>
</Border>
</esri:GraphicsLayer.MapTip>
</esri:GraphicsLayer>
Once again sorry for the confusion I guess I'm a little lost; if this is not what you want can you post your needs again and I'll take a look.ThanksJ