vb.net - VB.NET Sqlite DBNull 异常

Question

我在这里遇到问题，但我看不出哪里出错了。

问题是我在插入过程中插入了一个有效的整数值，但是当我检索该值时，我在这一行中得到一个 DBNull 异常：

iTestValue = rTest("myscore")

完整代码如下：

    Dim nCn As SQLiteConnection
    ncn = New SQLiteConnection("Data Source=:memory:")
    ncn.Open()

    Dim cmdCreate1 As New SQLiteCommand(nCn)
    cmdCreate1.CommandText = "CREATE TABLE mytable (mytext TEXT,myscore INTEGER)"
    cmdCreate1.ExecuteNonQuery()
    cmdCreate1.CommandText = "CREATE INDEX idx_mytable_myscore ON mytable (myscore)"
    cmdCreate1.ExecuteNonQuery()

    Dim nTA As SQLiteTransaction
    nTA = nCn.BeginTransaction

    Dim nCmdIns As New SQLiteCommand("INSERT INTO mytable (mytext,myscore) VALUES (?,?)", nCn)

    Dim l&
    For l = 1 To UBound(uNPhones)
        nCmdIns.Parameters.Clear()
        nCmdIns.Parameters.Add(ExpandCat(uNPhones(l).Text), DbType.String)
        nCmdIns.Parameters.Add(uNPhones(l).Score, DbType.Int32)
        nCmdIns.ExecuteNonQuery()
        Application.DoEvents()
    Next l

    nTA.Commit()

    Dim nSelTest As New SQLiteCommand("SELECT * FROM mytable", nCn)
    Dim rTest As SQLiteDataReader
    rTest = nSelTest.ExecuteReader

    Dim iCountTest As Integer
    iCountTest = 0

    Do While rTest.Read
        Dim iTestValue As Integer
        iTestValue = rTest("myscore")
        Dim sTestValue As String
        sTestValue = rTest("mytext")
        iCountTest += 1
    Loop