DesignInstance not working in VS2012

Question

I just spent several hours on an issue when using VS2012, WPF 4.5 and design-time data, specifically the DesignInstance attribute.

Goal: I wanted to have design-time data support in my WPF project (MVVM-based), both in VS2012 and Blend, and I could not for the life of me make the MVVMLight approach work consistently.

So I tried to change to "just" using the built-in support for design-time data, using the markup extension provided with Blend.

Problem: Consider the following code:

<Window x:Class="Nova.View.AlertsView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:local="clr-namespace:Nova.View"
        xmlns:vm="clr-namespace:Nova.ViewModel"
        mc:Ignorable="d"
        DataContext="{Binding Alerts, Source={StaticResource Locator}}" 
        d:DataContext="{d:DesignInstance vm:DesignAlertsViewModel, IsDesignTimeCreatable=True}"
... />

Both VS2012 and Blend reports "the name DesignAlertsViewModel does not exist in the namespace clr-namespace:Nova.ViewModel", even though intellisense resolves it just fine, and you have checked a thousand times that the namespace and class name are both correct.

Answer 1

I ran into this error myself in VS2013 then found this question. After searching more, I found an answer that helped me solve it.

instead of

d:DataContext="{d:DesignInstance vm:DesignAlertsViewModel, IsDesignTimeCreatable=True}"

use

d:DataContext="{d:DesignInstance d:Type=vm:DesignAlertsViewModel, IsDesignTimeCreatable=True}"

I was using "...d:DesignInstance Type=vm:..." and that displays the same error described above. As soon as I add "d:" everything works.

Here is the thread I found that helped.

https://stackoverflow.com/a/21690404/2892400