Question

我需要检查文件（扩展名未知）是否是有效的SQLite数据库。

我的功能正常，但是当它失败时，退出函数后文件仍然被锁定：

Public Function IsSqliteDB(ByVal uPath As String) As Boolean

    'Workaround for my problem: Make a copy and work on this because this function is going to lock the file unfortunately
    Dim sNewPath As String
    sNewPath = Settings.Locations.Folder_LocalAppData_Temp & "\temp_" & Replace(Now.ToString, ":", "_") & ".db"

    modIO.FileForceCopy(uPath, sNewPath)

    Dim bIsSQLiteDB As Boolean = False

    Dim c As New dhRichClient3.cConnection
    Dim r As dhRichClient3.cRecordset


    Try
        Dim b As Boolean = c.OpenDB(sNewPath) 'returns true although this is not an sqlite-db. Can't do anything about it
        R = c.OpenRecordset("SELECT * FROM sqlite_master")
        bIsSQLiteDB = True

    Catch ex As Exception
        r = Nothing
        c = Nothing
    Finally
        r = Nothing
        c = Nothing
    End Try

    modIO.DeleteFile(sNewPath)'this fails. File is locked

    Return bIsSQLiteDB

End Function

有人看到我可以确保文件不再被锁定的位置吗？或者我真的必须使用该文件的副本，因为COM组件的行为并不是真的已知（不幸的是闭源）？我确实可以使用备份，但文件可能非常大（> 1 GB），所以如果我能避免它，我想避免复制工作。

dhRichClient中没有“关闭”功能。我想，一旦cConection超出范围，就会在内部调用“关闭”。在函数末尾调用GC.Collect（）没有帮助。

Answer 1

要确定文件是否是SQLite数据库，只需检查database header的前16个字节。

来自tmighty的评论：

Public Function IsSqliteDB(ByVal uPath As String) As Boolean
    Dim bytes(16) As Byte
    Using fs As New IO.FileStream(uPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
        fs.Read(bytes, 0, 16)
    End Using
    Dim text As String = System.Text.ASCIIEncoding.ASCII.GetString(bytes)
    Return text.Contains("SQLite format")
End Function

检查文件是否是有效的SQLite数据库

1 个答案: