[英]Cannot create a table without columns error Xamarin SQLite
我正在尝试在我的 Xamarin 应用程序中使用本地 SQLite 数据库,我一直在关注本教程: https-docs.microsoft.com/en-usx/ =vswin
加载我正在测试它的 ListView 页面时,我总是收到错误:System.AggregateException:'发生了一个或多个错误。 (不能创建没有列的表('TestApp1.Piece' 有公共属性吗?))'
这是适用的代码:
片断.cs
namespace TestApp1
{
public class Piece
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public int PartNum { get; set; }
public string Category { get; set; }
public string Url { get; set; }
}
}
PieceDatabase.cs
namespace TestApp1
{
public class PieceDatabase
{
readonly SQLiteAsyncConnection _database;
public PieceDatabase(string dbPath)
{
_database = new SQLiteAsyncConnection(dbPath);
_database.CreateTableAsync<Piece>().Wait();
}
public Task<List<Piece>> GetPieceAsync()
{
return _database.Table<Piece>().ToListAsync();
}
public Task<int> SavePieceAsync(Piece temp)
{
return _database.InsertAsync(temp);
}
}
}
App.xaml.cs
namespace TestApp1
{
public partial class App : Application
{
static PieceDatabase database;
public static PieceDatabase PieceDatabase
{
get
{
if (database == null)
{
database = new PieceDatabase(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "pieces.db3"));
}
return database;
}
}
public App()
{
InitializeComponent();
MainPage = new NavigationPage(new Page1());
}
protected override void OnStart()
{
// Handle when your app starts
}
protected override void OnSleep()
{
// Handle when your app sleeps
}
protected override void OnResume()
{
// Handle when your app resumes
}
}
}
数据库Test.xaml.cs
namespace TestApp1
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class DatabaseTest : ContentPage
{
protected override async void OnAppearing()
{
base.OnAppearing();
/** The error does not occur if I add a piece here, but I'm trying to figure out why that is
await App.PieceDatabase.SavePieceAsync(new Piece
{
Category = "Beams",
PartNum = 1,
Url = "whatever.com"
}); */
List<Piece> test = await App.PieceDatabase.GetPieceAsync();
listView.ItemsSource = test;
}
public DatabaseTest()
{
InitializeComponent();
}
async void Handle_ItemTapped(object sender, ItemTappedEventArgs e)
{
if (e.Item == null)
return;
await DisplayAlert("Item Tapped", "An item was tapped.", "OK");
//Deselect Item
((ListView)sender).SelectedItem = null;
}
}
}
数据库Test.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="TestApp1.DatabaseTest">
<StackLayout Margin="20,35,20,20">
<ListView x:Name="listView">
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding PartNum}"
Detail="{Binding Url}"
/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</ContentPage>
这是我第一次与 Xamarin 合作,因此感谢您的帮助或解释。
我做了一个关于从 sqlite 数据库加载数据的示例,您从 github 下载它,我没有问题,我使用 sqlite-net-pcl 1.6.258-beta 版本和 Z625CF3DD56A2CEE259D91639B445。
https://github.com/CherryBu/Sqlite-Listview
您还可以查看以下有关详细信息的文章:
https://www.c-sharpcorner.com/article/xamarin-forms-sqlite-database-crud-operations2/
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