Question

I’m trying to see a form developed by someone else (ex-employee) in Visual Studio 2008 but keep running into the following error when I try and look at MainForm.xaml (it fails to load in the designer view):

Error Could not create an instance of type ‘NumericTextBox’. D:\MySolution\GUI\MainForm.xaml

My solution is organised something like this (shortened for brevity – it’s the last line of this where the error occurs):

\solution
    \Gui
        \App.xaml
        \MainForm.xaml
    \Utils
        \NumericTextBox.cs

My MainForm.xaml looks something like this:

<Window x:Class="MyCompany.MyDepartment.MyProject.MainForm"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:MyCompany.MyDepartment.MyProject"
        xmlns:myproject="clr-namespace:MyCompany.MyDepartment.MyProject;assembly=MyProject"
        xmlns:dsp="clr-namespace:MyCompany.MyDepartment.MyProject.DSP;assembly=MyProject"
        xmlns:filters="clr-namespace:MyCompany.MyDepartment.DSP.Filters;assembly=DSP"
        xmlns:mydepartment="clr-namespace:MyCompany.MyDepartment.Utils;assembly=Utils"
        xmlns:scope="clr-namespace:MyCompany.MyDepartment;assembly=ScopeControl"
        Title="MyProject" Height="900" Width="1024"
        Loaded="Window_Loaded"
        Closing="Window_Closing" ResizeMode="CanResize" Icon="/MyProjectGUI;component/MyProjectGUI.ico">

    <Window.Resources>
    ...
    </Window.Resources>

    <DockPanel>
        <StackPanel DockPanel.Dock="Left" CanVerticallyScroll="True" CanHorizontallyScroll="False">
            <GroupBox Name="SensorControlGroup"  Header="Sensor Control">
            ...
            </GroupBox>
            <GroupBox Header="Sensor State">
                <StackPanel Name="SensorStackPanel">
                    <Expander Name="EnvironmentExpander" Header="Environment">
                    ...
                    </Expander>
                    <Expander Name="SynthExpander" Header="Synthesiser" IsExpanded="True">
                        <Border Margin="2" Background="White" Padding="3">
                            <Grid>                                
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="120"/>
                                    <ColumnDefinition Width="60"/>
                                    <ColumnDefinition Width="60"/>
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                    <RowDefinition/>
                                </Grid.RowDefinitions>
                                <Label Grid.Column="0" Grid.Row="0">Frequency (MHz):</Label>

                                <mydepartment:NumericTextBox Grid.Column="1"
                                                     x:Name="SynthFrequency" DecimalPlaces="3"
                                                     Maximum="0" Minimum="0" />

What might cause that error? Everything compiles okay but the application crashes when I run it. I was hoping the two problems might be a related issue.

Answer 1

Okay, so it turned out that although Visual Studio was set up to use v3.5 of the .net framework you need to seperately install v3.5 of the framework – it seems I only had v2 installed. Let this be a lesson for anyone else struggling with the same problems!