SQLite.Net不会在Win IoT Library中创建 [英] SQLite.Net Won't Create In Win IoT Library
问题描述
我一直在努力寻找一种在Win IoT下在Pi上持久保存SQLite数据库的方法，该方法可以由不同的后台应用程序访问(不能同时使用).
I have been struggling to find a way of persisting an SQLite database on a Pi under Win IoT which can be accessed by different background applications (not concurrently).
当我发现图书馆(音乐，图片，视频-但反而没有文件，而没有更多工作)时，我以为我找到了答案.我可以在一个应用程序中创建一个文本文件，并将其写入图片库的默认文件夹.然后，我可以使用另一个应用程序读取文本文件. File.Exists返回true.宾果游戏(我认为)！
I thought I had the answer when I discovered Libraries (Music, Pictures, Videos - but perversely not Documents, without more work). I can create a text file in one app and write it to the Pictures library's default folder. I can then read the text file with another app. File.Exists returns true. Bingo (I thought)!
但是，SQLite不会在该文件夹中创建数据库，也不会打开我复制到该文件夹中的现有数据库. SQLite.Net.SQLiteConnection返回一个SQLite异常:无法打开数据库文件:C:\ Data \ Users \ DefaultAccount \ Pictures \ MyDb.db(CannotOpen)"-没有其他线索.
However, SQLite will not create a database in the folder or open an existing database that I copy to the folder. SQLite.Net.SQLiteConnection returns an SQLite exception: "Could not open database file: C:\Data\Users\DefaultAccount\Pictures\MyDb.db (CannotOpen)" - no further clues.
该文件夹似乎授予了全部权限.请问有人有什么想法吗?
The folder appears to grant full permissions. Does anyone have any ideas, please?
创建和编写文本文件:
using System;
using Windows.ApplicationModel.Background;
using System.IO;
using System.Diagnostics;
//*** NOTE: Pictures Library checked in Package.appxmanifest 'Capabilities'
namespace LibraryTest
{
public sealed class StartupTask : IBackgroundTask
{
private BackgroundTaskDeferral Deferral;
public async void Run (IBackgroundTaskInstance taskInstance)
{
Deferral = taskInstance.GetDeferral ();
var myPictures = await Windows.Storage.StorageLibrary.GetLibraryAsync
(Windows.Storage.KnownLibraryId.Pictures);
string path = myPictures.SaveFolder.Path;
Debug.WriteLine ($"'Pictures' Folder: {path}");
string newFilePath = Path.Combine (path, "TestTextFile.txt");
Debug.WriteLine ($"New File Path: {newFilePath}");
try {
using ( var stream = File.OpenWrite (newFilePath) ) {
using ( var writer = new StreamWriter (stream) ) {
writer.Write ("This is some test text.");
}
}
Debug.WriteLine ($"File created OK");
}
catch (Exception ex) { Debug.WriteLine ($"Exception: {ex.Message}"); }
}
}
}
生产:
'Pictures' Folder: C:\Data\Users\DefaultAccount\Pictures
New File Path: C:\Data\Users\DefaultAccount\Pictures\TestTextFile.txt
File created OK
阅读:
using System;
using Windows.ApplicationModel.Background;
using System.IO;
using System.Diagnostics;
//*** NOTE: Pictures Library checked in Package.appxmanifest 'Capabilities'
namespace ReadLibraryTest
{
public sealed class StartupTask : IBackgroundTask
{
private BackgroundTaskDeferral Deferral;
public async void Run (IBackgroundTaskInstance taskInstance)
{
Deferral = taskInstance.GetDeferral ();
var myPictures = await Windows.Storage.StorageLibrary.GetLibraryAsync
(Windows.Storage.KnownLibraryId.Pictures);
string path = myPictures.SaveFolder.Path;
Debug.WriteLine ($"'Pictures' Folder: {path}");
string newFilePath = Path.Combine (path, "TestTextFile.txt");
Debug.WriteLine ($"New File Path: {newFilePath}");
try {
using ( var stream = File.OpenRead (newFilePath) ) {
using ( var reader = new StreamReader (stream) ) {
string fileContents = reader.ReadLine ();
Debug.WriteLine ($"First line of file: '{fileContents}'");
}
}
Debug.WriteLine ($"File read OK");
}
catch ( Exception ex ) { Debug.WriteLine ($"Exception: {ex.Message}"); }
}
}
}
生产:
'Pictures' Folder: C:\Data\Users\DefaultAccount\Pictures
New File Path: C:\Data\Users\DefaultAccount\Pictures\TestTextFile.txt
First line of file: 'This is some test text.'
File read OK
推荐答案
但是，SQLite不会在该文件夹中创建数据库或打开 我复制到该文件夹的现有数据库. SQLite.Net.SQLiteConnection返回一个SQLite异常:无法 打开数据库文件:C:\ Data \ Users \ DefaultAccount \ Pictures \ MyDb.db (CannotOpen)"-没有其他线索.
However, SQLite will not create a database in the folder or open an existing database that I copy to the folder. SQLite.Net.SQLiteConnection returns an SQLite exception: "Could not open database file: C:\Data\Users\DefaultAccount\Pictures\MyDb.db (CannotOpen)" - no further clues.
是的，我转载了这个问题.看来此文件夹不适用于SQLite文件操作，但我不知道问题出在哪里.
Yes, I reproduced this issue. It seems this folder does not work with SQLite file operations but I don't know where the problem is.
作为一种解决方法，您可以使用 PublisherCacheFolder .我创建.db文件，并在一个后台应用程序中写入数据.并从另一个后台应用程序读取数据.有用.
As a workaround, you can use PublisherCacheFolder. I create the .db file and write data in one background app. And read the data from another background app. It works.
联系方式:
public sealed class Contact
{
public int Id { get; set; }
public string Name { get; set; }
}
创建和写入文件
StorageFolder sharedFonts = Windows.Storage.ApplicationData.Current.GetPublisherCacheFolder("test");
var sqlpath = System.IO.Path.Combine(sharedFonts.Path, "MyDb.db");
using (SQLite.Net.SQLiteConnection conn = new SQLite.Net.SQLiteConnection(new SQLite.Net.Platform.WinRT.SQLitePlatformWinRT(), sqlpath))
{
conn.CreateTable<Contact>();
for (var i = 0; i < 100; i++)
{
Contact contact = new Contact()
{
Id = i,
Name = "A"
};
conn.Insert(contact);
}
}
读取文件:
StorageFolder sharedFonts = Windows.Storage.ApplicationData.Current.GetPublisherCacheFolder("test");
var sqlpath = System.IO.Path.Combine(sharedFonts.Path, "MyDb.db");
using (SQLite.Net.SQLiteConnection conn = new SQLite.Net.SQLiteConnection(new SQLite.Net.Platform.WinRT.SQLitePlatformWinRT(), sqlpath))
{
var query = conn.Table<Contact>().Where(v => v.Name.Equals("A"));
foreach (var stock in query)
Debug.WriteLine("contact: " + stock.Id);
}
要使用此发布者文件夹，您需要在Package.appxmanifest中添加以下行:
To use this publisher folder you need add the following lines in Package.appxmanifest:
<Extensions>
<Extension Category="windows.publisherCacheFolders">
<PublisherCacheFolders>
<Folder Name="test" />
</PublisherCacheFolders>
</Extension>
</Extensions>
这篇关于SQLite.Net不会在Win IoT Library中创建的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
