异步 GetFiles 并写入 Sqlite 数据库

Question

我有一个软件，我想在其中获取列表中的所有文件，然后将它们写入 sqlite 数据库。但是当我调用该方法时，它会阻塞主 UI，即使我尝试执行一些等待任务。我究竟做错了什么？这是我的代码：

这是当窗口加载时，我调用方法来获取文件列表并将其放入我正在创建的 sqlite 数据库中。

Private Async Function MainWindow_Loaded() As Task
        Try
            InitializeComponent()

                Await CreateFileList()          

        Catch ex As Exception
            WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
        End Try

    End Function



Create the filelist and put it into sqlite database function. It should be async but something wrong with it.

Private Async Function CreateFileList() As Task
        Try

            lblState1.Content = "Create File List"

            If Directory.Exists(System.AppDomain.CurrentDomain.BaseDirectory & "filelist") Then
                Directory.Delete(System.AppDomain.CurrentDomain.BaseDirectory & "filelist", True)
            End If

            Dim tasks As List(Of Task) = New List(Of Task)()

            Dim t As Task = Task.Run(Sub()

                                         For Each path In Directory.GetFiles(System.AppDomain.CurrentDomain.BaseDirectory, "*.*", SearchOption.AllDirectories)
                                             FilesList.Add(path)
                                         Next
                                     End Sub)
            tasks.Add(t)
            Task.WaitAll(tasks.ToArray)

            Database.DbCreator.createDbFile("filelist", "filelist.db3")

            Database.DbCreator.createDbConnection("filelist\filelist.db3")

            If Database.DbCreator.checkIfTableExist("filelist") = False Then

                Dim create_table As String = String.Empty


                create_table &= "CREATE TABLE IF NOT EXISTS filelist ("
                create_table &= "id INTEGER PRIMARY KEY NOT NULL,"
                create_table &= "filepath TEXT NOT NULL,"
                create_table &= "filesize TEXT NOT NULL DEFAULT 0,"
                create_table &= "needstobedone INTEGER NOT NULL DEFAULT 0,"
                create_table &= "todownload INTEGER NOT NULL DEFAULT 0)"

                Await Database.DbCreator.SqlNewQuery(create_table)

            End If


            Dim i As Integer = 1
            For Each file As String In FilesList
                If Not file.Contains("/Updates/") Or Not file.Contains("/filelist/") Or Not file.Contains("/lic/") Then
                    varPercent = Math.Round(i / FilesList.Count * 100)
                    Dim filesize As Long = New FileInfo(file).Length

                    Dim InsertQuery As String = ""
                    InsertQuery &= "INSERT INTO filelist (filepath, filesize) VALUES "
                    InsertQuery &= String.Format("('{0}','{1}')", file.Replace(System.AppDomain.CurrentDomain.BaseDirectory, ""), filesize)

                    Await Database.DbCreator.SqlNewQuery(InsertQuery)

                    i = i + 1
                End If
            Next

            Database.DbCreator.closeDbConnection("filelist\filelist.db3")

        Catch ex As Exception
            WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
        End Try
    End Function

My Database Creators functions, it should be async as well. Any suggestion on this way?

Namespace Database
    Public Class DbCreator
        Public Shared dbConnection As SQLiteConnection
        Public Shared command As New SQLiteCommand
        Public Shared sqlCommand As String
        Public Shared dbPath As String = System.AppDomain.CurrentDomain.BaseDirectory
        Public Shared dbFilePath As String

        Public Shared Sub createDbFile(dir As String, name As String)
            Try
                If Not String.IsNullOrEmpty(name) AndAlso Not Directory.Exists(dbPath & dir) Then Directory.CreateDirectory(dbPath & dir)
                dbFilePath = dbPath & "\" & dir & "\" & name

                If Not File.Exists(dbFilePath) Then
                    SQLiteConnection.CreateFile(dbFilePath)
                End If
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
            End Try
        End Sub

        Public Shared Function createDbConnection(name) As String
            Dim strCon As String = String.Format("Data Source={0};", System.AppDomain.CurrentDomain.BaseDirectory & name)
            Try
                dbConnection = New SQLiteConnection(strCon)
                dbConnection.Open()
                command = dbConnection.CreateCommand()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
            End Try
            Return strCon
        End Function

        Public Shared Function DbConnect(name) As SQLiteConnection
            Dim strCon As String = String.Format("Data Source={0};", System.AppDomain.CurrentDomain.BaseDirectory & name)
            Try
                dbConnection = New SQLiteConnection(strCon)
                dbConnection.Open()
                command = dbConnection.CreateCommand()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
            End Try
            Return dbConnection
        End Function

        Public Shared Function closeDbConnection(name) As String
            Dim strCon As String = String.Format("Data Source={0};", System.AppDomain.CurrentDomain.BaseDirectory & name)
            Try
                dbConnection = New SQLiteConnection(strCon)
                dbConnection.Close()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Hiba: " & ex.ToString)
            End Try
            Return strCon
        End Function

        Public Shared Async Function SqlNewQuery(command As String) As Task
            Try
                sqlCommand = command
                Await executeQuery(sqlCommand)
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
            End Try
        End Function

        Public Shared Function checkIfTableExist(ByVal tableName As String) As Boolean
            Dim result As Object = Nothing
            command.CommandText = ""
            Try
                command.CommandText = "SELECT name FROM sqlite_master WHERE name='" & tableName & "'"
                result = command.ExecuteScalar()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Hiba: " & ex.ToString)
            End Try
            Return If(result IsNot Nothing AndAlso result.ToString() = tableName, True, False)
        End Function

        Public Shared Async Function executeQuery(ByVal sqlCommand As String) As Task
            Try
                Dim triggerCommand As SQLiteCommand = dbConnection.CreateCommand()
                triggerCommand.CommandText = sqlCommand
                Await triggerCommand.ExecuteNonQueryAsync()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Error: " & ex.ToString)
            End Try
        End Function

        Public Shared Function checkIfTableContainsData(ByVal tableName As String) As Boolean
            Dim result As Object = Nothing
            Try
                command.CommandText = "SELECT count(*) FROM " & tableName
                result = command.ExecuteScalar()
            Catch ex As Exception
                WriteLog(DateTime.Now.ToString & " Hiba: " & ex.ToString)
            End Try
            Return If(Convert.ToInt32(result) > 0, True, False)
        End Function

    End Class
End Namespace

Answer 1

Task.WaitAll(tasks.ToArray)

会阻塞你的 UI 线程，你应该等待异步方法的结果。没有 Directory.GetFilesAsync 方法，所以最终你应该白化你自己的代码。

Dim filesList As List(Of String) = Await Task(Of List(Of String)).Run(
Function()
    Dim files As List(Of String) = New List(Of String)()
    For Each path In Directory.GetFiles(System.AppDomain.CurrentDomain.BaseDirectory, "*.*", SearchOption.AllDirectories)
        files.Add(path)
    Next
    Return files
End Function)