Question

我将SQLite数据库名称存储在App.config中，并使用System.Configuration参考来检索数据库名称
我认为这没有任何价值，因此删除了readConfig代码
现在我无法创建数据库及其两个表
有人会友好地检查下面的代码并解释我做错了吗？

在模块中设置

Public gv_dbName As String = "Notes.db"

frmStart的顶层声明

Public connStr As String = "Data Source={0};Version=3;"
Public conn As SqliteConnection
Dim cmd As SqliteCommand

其他相关代码

    Private Sub frmStart_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Icon = Icon.ExtractAssociatedIcon(Application.ExecutablePath)
    connStr = String.Format(connStr, gv_dbName)

    If My.Computer.FileSystem.FileExists(gv_dbName) Then
        btnCreate.Visible = False
        btnToEnterData.Visible = True
        btnToViewParentTable.Visible = True
    ElseIf Not My.Computer.FileSystem.FileExists(gv_dbName) Then
        conn = New SqliteConnection($"Data Source = '{gv_dbName}';Version=3;")
        tbMessage.Text = "Created Database & Tables"
    End If

End Sub

Private Sub btnCreate_Click(sender As Object, e As EventArgs) Handles btnCreate.Click
    makeDB()
End Sub

Public Sub makeDB()

    If Not My.Computer.FileSystem.FileExists(gv_dbName) Then
        Try
            conn = New SqliteConnection($"Data Source = '{gv_dbName}';Version=3;")
            conn.Open()
            makeParentTable()
            makeChildTable()
            conn.Close()
        Catch ex As Exception
            tbMessage.Text = "Database NOT Created"
        End Try
    End If

End Sub

我什至尝试了frmStart的最高级别

'Friend gv_dbName As String = "Notes.db"

这是我基于此代码编写的内容
Link to Code

Answer 1

假设Notes.db位于应用程序目录（exe所在的目录）中，这就是在sqlite上打开连接的方式。只需删除不需要的选项即可。

New=True

如果Open（）失败，则可以尝试在连接字符串中添加conn = New SQLiteConnection(strConString & "New=True;")

newArr.push({})

Answer 2

使用Microsoft.Data.Sqlite.Core或System.Data.SQLite （Db版本3） 可以确定文件是否存在。只需给出一个 物理/绝对 路径，如果不存在，则创建一个新文件named.db，否则，现有数据库返回：

示例：

Friend dbPath As String = IO.Path.Combine(Application.StartupPath, "Notes.db")

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    TestMySqlite()
End Sub


Private Sub TestMySqlite()
    Try

        'You can use this but it is not important for version 3 as is auto created the new file by itself
        'If Not IO.File.Exists(dbPath) Then SQLiteConnection.CreateFile(dbPath)

        Using conn As SQLiteConnection = New SQLiteConnection("Data Source=" & dbPath & "; Version=3;")

            conn.Open()
            Console.WriteLine(conn.FileName)

            Using command As SQLiteCommand = New SQLiteCommand("CREATE TABLE IF NOT EXISTS  Test (RowIndex INTEGER PRIMARY KEY AUTOINCREMENT COLLATE NOCASE, name varchar(20))", conn)
                command.ExecuteNonQuery()
            End Using

            Using cmdInsert = New SQLiteCommand("INSERT INTO Test (name) values ('this is a test')", conn)
                cmdInsert.ExecuteNonQuery()
            End Using

        End Using

    Catch ex As Exception
        Console.WriteLine(ex.ToString)
        Stop
    End Try

End Sub

在此示例中，将在您的应用程序正在运行的文件夹下创建一个名为Notes.db的文件（如果不存在）。下次调用SQLiteConnection只是返回Notes.db

未创建SQLite数据库创建

2 个答案: