Javascript – Node.js says it can’t load sqlite3 module, but does anyway

Using npm install installs the module into the current directory only (in a subdirectory called node_modules). Is app.js located under home/dave/src/server/? If not and you want to use the module from any directory, you need to install it globally using npm install -g.

I usually install most packages locally so that they get checked in along with my project code.

Update (8/2019):

Nowadays you can use package-lock.json file, which is automatically generated when npm modifies your node_modules directory. Therefore you can leave out checking in packages, because the package-lock.json tracks the exact versions of your node_modules, you're currently using. To install packages from package-lock.json instead of package.json use the command npm ci.

Update (3/2016):

I've received a lot of flak for my response, specifically that I check in the packages that my code depends on. A few days ago, somebody unpublished all of their packages (https://kodfabrik.com/journal/i-ve-just-liberated-my-modules) which broke React, Babel, and just about everything else. Hopefully it's clear now that if you have production code, you can't rely on NPM actually maintaining your dependencies for you.

You can definitely achieve your goal but you need to take a different approach.

In your solution you're trying to have a dependency property for of a UIElement - and since it never gets set and default value is null that's why you get a NullReference exception. You could probably go ahead by changing the default value from null to new TextBox or something like that but even if it did work it still would feel like a hack.

In Silverlight you have to implement Dpendency Properties yourself. However you've not implemented them as they should be - I tend to use this dependency property generator to do so.

One of the great things about DPs is that they support change notification. So with that in mind all you have to do to get your sample working is define to DPs: ItemContent and ListContent with the same type as Content (object) and when the framework notifies you that either of them has been changed, simply update your textboxes! So here is the code to do this:

MultiContent.xaml:

   <Grid x:Name="LayoutRoot" Background="White">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="100" />
            <ColumnDefinition Width="100" />
        </Grid.ColumnDefinitions>
        <ContentControl x:Name="pnlList" Grid.Column="0" />
        <ContentControl x:Name="pnlItem" Grid.Column="1" />
    </Grid>    

MultiContent.xaml.cs:

namespace MultiContent
{
    public partial class MultiContent : UserControl
    {
        #region ListContent

        /// <summary>
        /// ListContent Dependency Property
        /// </summary>
        public object ListContent
        {
            get { return (object)GetValue(ListContentProperty); }
            set { SetValue(ListContentProperty, value); }
        }
        /// <summary>
        /// Identifies the ListContent Dependency Property.
        /// </summary>
        public static readonly DependencyProperty ListContentProperty =
            DependencyProperty.Register("ListContent", typeof(object),
            typeof(MultiContent), new PropertyMetadata(null, OnListContentPropertyChanged));

        private static void OnListContentPropertyChanged
          (object sender, DependencyPropertyChangedEventArgs e)
        {
            MultiContent m = sender as MultiContent;
            m.OnPropertyChanged("ListContent");
        }

        #endregion

        #region ItemContent

        /// <summary>
        /// ItemContent Dependency Property
        /// </summary>
        public object ItemContent
        {
            get { return (object)GetValue(ItemContentProperty); }
            set { SetValue(ItemContentProperty, value); }
        }
        /// <summary>
        /// Identifies the ItemContent Dependency Property.
        /// </summary>
        public static readonly DependencyProperty ItemContentProperty =
            DependencyProperty.Register("ItemContent", typeof(object),
            typeof(MultiContent), new PropertyMetadata(null, OnItemContentPropertyChanged));

        private static void OnItemContentPropertyChanged
          (object sender, DependencyPropertyChangedEventArgs e)
        {
            MultiContent m = sender as MultiContent;
            m.OnPropertyChanged("ItemContent");
        }

        #endregion

        /// <summary>
        ///  Event called when any chart property changes
        ///  Note that this property is not used in the example but is good to have if you plan to extend the class!
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        ///  Called to invoke the property changed event
        /// </summary>
        /// <param name="propertyName">The property that has changed</param>
        protected void OnPropertyChanged(string propertyName)
        {
            if (propertyName == "ListContent")
            {
                // The ListContent property has been changed, let's update the control!
                this.pnlList.Content = this.ListContent;
            }
            if (propertyName == "ItemContent")
            {
                // The ListContent property has been changed, let's update the control!
                this.pnlItem.Content = this.ItemContent;
            }
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public MultiContent()
        {
            InitializeComponent();
        }
    }
}

MainPage.xaml:

    <Grid x:Name="LayoutRoot" Background="White">
        <local:MultiContent>
            <local:MultiContent.ListContent>
                <ListBox x:Name="lstListOfStuff" Width="50" Height="50" />
            </local:MultiContent.ListContent>
            <local:MultiContent.ItemContent>
                <TextBox x:Name="txtItemName" Width="50" />
            </local:MultiContent.ItemContent>
        </local:MultiContent>
    </Grid>

This should do the trick!