Workflow1.xaml

<p:Activity x:Class="Nullables.Workflow1"  
          mc:Ignorable="sap2010"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          sap2010:ExpressionActivityEditor.ExpressionActivityEditor="C#"
          xmlns:sap2010="http://schemas.microsoft.com/netfx/2010/xaml/activities/presentation"
          xmlns:sco="clr-namespace:System.Collections.ObjectModel;assembly=mscorlib" 
          xmlns:p="http://schemas.microsoft.com/netfx/2009/xaml/activities"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> 
    <p:TextExpression.NamespacesForImplementation>
        <sco:Collection x:TypeArguments="x:String">
            <x:String>System</x:String>
            <x:String>System.Collections.Generic</x:String>
            <x:String>System.Data</x:String>
            <x:String>System.Linq</x:String>
            <x:String>System.Text</x:String>
        </sco:Collection>
    </p:TextExpression.NamespacesForImplementation>
    <p:TextExpression.ReferencesForImplementation>
        <sco:Collection x:TypeArguments="p:AssemblyReference">
            <p:AssemblyReference>mscorlib</p:AssemblyReference>
            <p:AssemblyReference>System</p:AssemblyReference>
            <p:AssemblyReference>System.Core</p:AssemblyReference>
            <p:AssemblyReference>System.Data</p:AssemblyReference>
            <p:AssemblyReference>System.ServiceModel</p:AssemblyReference>
            <p:AssemblyReference>System.Xml</p:AssemblyReference>
        </sco:Collection>
    </p:TextExpression.ReferencesForImplementation>
</p:Activity>