Question

我创建了一个应用程序，它最初会创建一个数据库并在其中保存一些数据。现在，我想在用户点击重置按钮时删除此数据库及其文件，但我收到错误 - “这是在另一个进程中使用”。我希望它在单击重置按钮时删除并重新创建数据库。有什么想法吗？

Answer 1

最常见的原因是与Windows Phone上的独立存储交互的线程不安全性质。无论您如何实现数据库（无论是文件还是文件系列），您都会在某种程度上与隔离存储进行交互。

我强烈建议您阅读，并确保在走得太远之前理解this overview of isolated storage。

你说的是：

这在另一个过程中使用

让我觉得你正在使用第三方库来做你的数据库。当库本身无法访问隔离存储时，会抛出此异常/错误。如果不确切知道如何实施数据库，很难准确地说出你的情况。

您永远不会“重新创建IsolatedStorage”，“隔离存储”是一个术语，用于定义应用程序可以访问的磁盘空间集合。与文件夹非常相似，此磁盘空间具有根，并且仅包含您创建的文件。

为了在访问独立存储时避免线程异常，请确保在C＃中使用using关键字，如下所示：

namespace IsolatedStorageExample
{
    public class ISOAccess
    {
        // This example method will read a file inside your Isolated Storage.
        public static String ReadFile(string filename)
        {
            string fileContents = "";
            // Ideally, you should enclose this entire next section in a try/catch block since
            // if there is anything wrong with below, it will crash your app.
            // 
            // This line returns the "handle" to your Isolated Storage. The phone considers the
            // entire isolated storage folder as a single "file", which is why it can be a 
            // little bit of a confusing name.
            using(IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForAppliaction())
            {   
                // If the file does not exist, return an empty string
                if(file.Exists(filename))
                {
                    // Obtain a stream to the file
                    using(IsolatedStorageFileStream stream = File.OpenFile(filename, FileMode.Open)
                    {
                        // Open a stream reader to actually read the file.
                        using(StreamReader reader = new StreamReader(stream))
                        {
                            fileContents = reader.ReadToEnd();
                        }
                    }
                }   
            }

            return fileContents;
        }
    }
}

这应该有助于解决您的线程安全问题。要更具体地帮助您完成您想要做的事情，请查看以下方法（您可以将其添加到上述类中）：

// BE VERY CAREFUL, running this method will delete *all* the files in isolated storage... ALL OF THEM
public static void ClearAllIsolatedStorage()
{
    // get the handle to isolated storage
    using(IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication())
    {
        // Get a list of all the folders in the root directory
        Queue<String> rootFolders = new Queue<String>(file.GetDirectoryNames());

        // For each folder...
        while(0 != rootFolders.Count)
        {
            string folderName = rootFolders.Dequeue();

            // First, recursively delete all the files and folders inside the given folder.
            // This is required, because you cannot delete a non-empty directory
            DeleteFilesInFolderRecursively(file, folderName);

            // Now that all of it's contents have been deleted, you can delete the directory
            // itsself.
            file.DeleteDirectory(rootFolders.Dequeue());
        }

        // And now we delete all the files in the root directory
        Queue<String> rootFiles = new Queue<String>(file.GetFileNames());
        while(0 != rootFiles.Count)
            file.DeleteFile(rootFiles.Dequeue());
    }
}

private static void DeleteFilesInFolderRecursively(IsolatedStorageFile iso, string directory)
{
    // get the folders that are inside this folder
    Queue<string> enclosedDirectories = new Queue<string>(iso.GetDirectoryNames(directory));

    // loop through all the folders inside this folder, and recurse on all of them
    while(0 != enclosedDirectories.Count)
    {
        string nextFolderPath = Path.Combine(directory, enclosedDirectories.Dequeue());
        DeleteFilesInFolderRecursively(nextFolderPath);
    }

    // This string will allow you to see all the files in this folder.
    string fileSearch = Path.Combine(directory, "*");

    // Getting the files in this folder
    Queue<string> filesInDirectory = iso.GetFileNames(fileSearch);

    // Finally, deleting all the files in this folder
    while(0 != filesInDirectory.Count)
    {
        iso.DeleteFile(filesInDirectory.Dequeue());
    }
}

我强烈推荐的另一件事是实现使用“多线程单例模式”访问IsolatedStorage的类，如here.所述

希望这有帮助。代码是“按原样”提供的，我没有编译它，但是一般的概念都在那里，所以如果有什么不妥之处，请阅读MSDN文档以查看我在哪里学习。但我向你保证，大部分是从我的功能代码中复制而来的，因此它应该可以正常工作，只需很少的粉丝。

在wp7中重置应用程序设置

1 个答案: