UWP - C#: Save Uri into SQLite or how to convert string into Uri when I load a gridview?

Question

I have to use an Image for GridViewItem style, every GridViewItem represents an object saved in a SQLite database, when I save a new object into the db I have to select from a combobox which image it uses.

This is the definition of the Combobox:

<ComboBox x:Name="UriImage" Width="200" RelativePanel.Below="ActiveToggle">
      <ComboBoxItem Content="Element1" x:Name="element1" IsSelected="True"/>
      <ComboBoxItem Content="Element2" x:Name="element2"/>
      <ComboBoxItem Content="Element3" x:Name="element3"/>
</ComboBox>

Then I created this to match the corresponding URI of the image to each ComboBoxItem

string ImageUriString=""; 

if (UriImage.SelectedValuePath == "Element1")
      ImageUriString = "ms-appx:///Assets/Orchid_2_FF.png";
else if (UriImage.SelectedValuePath == "Element2")
      ImageUriString = "ms-appx:///Assets/sapphire_orchid_FF.png";
else if (UriImage.SelectedValuePath == "Element3")
      ImageUriString = "ms-appx:///Assets/yellow-cowslip-orchid_FF.png";

Uri UriString = new Uri(ImageUriString, UriKind.RelativeOrAbsolute);

Then I added the Uri field to the class that represents the object when I try to save new object I have this Error: Don't know how to read System.Uri

To load the objects in the Gridview I use this:

private async void ReadAllSystemList_Loaded(object sender, RoutedEventArgs e)
{
   ReadAllSystemsList dbSystems = new ReadAllSystemsList();
   DB_FFSystems = await dbSystems.GetAllFFSystems(); //get all DB Systems       
   listBoxObj.ItemsSource = DB_FFSystems.OrderByDescending(i => i.ID).ToList();
}

and data Binding from Xaml.

<Image Width="350" Height="200" x:Name="ElementImage" Source="{Binding ImageUri}">

I thought about saving the URI as a string but how can I convert the string to Uri when loading the Gridview?

Answer 1

SQLite cannot store and parse URIs so that is the source of the error you are getting.

You can safely store string instead of Uri in the database. Usually the ideal approach is to have a simple class that is used as a database model (having a string property) and then another class that is used in the presentation layer and that will have Uri instead. This way you get a good separation of layers and can have a more practical interface on the presentation layer that is not limited by the database. You can even use libraries like Automapper to easily convert from one type to another instead of having to do it property by property.

However, if you don't want to deal with this, there are other options. First of all - you shouldn't have to convert from string to Uri at all when binding to Source of a Image . There is an implicit type conversion from string to Uri built into XAML, so it should work as expected.

Alternatively, you could implement a converter by creating a class deriving from IValueConverter . This whould override the Convert method and build a Uri instance from the passed in string . Then you register the converter as a resource with a x:Key and use it in code:

Source="{Binding ImageUri, Converter={StaticResource StringToUriConverter}"