Xamarin 表单中的本地 SQLite 数据库

Question

So I did an example Database outside Xamarin Forms using "DB Browser for SQLite" and put it in Assets File

and I'm trying to learn how to connect my Database to it so i did this :

XAML :

 <?xml version="1.0" encoding="utf-8" ?> <ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms/design" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="Behoerdensprache.Pages.FinanzAmt"> <ContentPage.Content> <StackLayout> <Label Text="Welcome to Xamarin.Forms!" VerticalOptions="CenterAndExpand" HorizontalOptions="CenterAndExpand" x:Name="LabelControl"/> <Entry Placeholder="Search" x:Name="SearchEntry"/> <Button Text="Press me" Clicked="Button_Clicked"/> </StackLayout> </ContentPage.Content> </ContentPage>

C# ButtonCode :

    private void Button_Clicked(object sender, EventArgs e)
    {
        SQLiteConnection conn = new SQLiteConnection(App.DataBaseLocation);
        conn.CreateTable<Wortschatz>();
        var gets = conn.Table<Wortschatz>().Where(i => i.Wort == SearchEntry.Text).ToString();
        LabelControl.Text = gets;

        conn.Close();

    }

App.DataBaseLocation is defined in the Mainactivity and AppDelegate :

in Mainactivity :

        string dbName = "BeamtenSprache.sqlite";
        string folderPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
        string fullPath = Path.Combine(folderPath, dbName);
        LoadApplication(new App(fullPath));

in AppDelegate :

        string dbName = "wortschatz.sqlite";
        string folderPath = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "..", "Library");
        string fullPath = Path.Combine(folderPath, dbName);
        LoadApplication(new App(fullPath));

new App(fullPath) this part i defined in App.cs :

 public static string DataBaseLocation = string.Empty;
    public App()
    {
        InitializeComponent();
        MainPage = new NavigationPage(new MainPage());
    }

    public App(string databaseLocation)
    {
        InitializeComponent();
        MainPage = new NavigationPage(new MainPage());
        DataBaseLocation = databaseLocation;
    }

but when i run the app and i press the Button this shows :

Answer 1

There is an Todo sample project in xamarin.forms.samples shows how to store and access data in a local SQLite database.

In Android project, he put the db file in Todo/Todo.Android/Resources/raw/

In iOS project, he put the db file in Todo/Todo.iOS/Resources/

And then he get the db path by:

public static class Constants
{
    public const string DatabaseFilename = "TodoSQLite.db3";

    public static string DatabasePath
    {
        get
        {
            var basePath = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
            return Path.Combine(basePath, DatabaseFilename);
        }
    }
}

You can download it and try with the code there in your project. For more information, you can read the document .

If you can't solve the problem, you can share your project here and I will check it:).