无法将数据存储到数据库

Question

执行查询时没有错误，但没有存储数据。可能有什么不对？

我的数据库是具有id，first_name，middle_name，last_name字段的员工。 id是自动编号，其余是短文本

我正在使用MS Access。

Imports System.Data.OleDb

Public Class AccountReg
    Dim dbProvider As String
    Dim dbSource As String
    Dim connString As String
    Dim myConnection As OleDbConnection = New OleDbConnection

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs)Handles Button1.Click
        dbProvider = "Provider=Microsoft.ACE.OLEDB.12.0;"
        dbSource = "Data Source=|DataDirectory|\PIA-AMS.accdb"
        connString = dbProvider & dbSource
        myConnection.ConnectionString = connString
        myConnection.Open()
        Dim str As String
        str = "INSERT INTO employee (first_name, middle_name, last_name) VALUES (?,?,?)"
        Dim cmd As OleDbCommand = New OleDbCommand(str, myConnection)
        cmd.Parameters.Add(New OleDbParameter("first_name", CType(TextBox1.Text, String)))
        cmd.Parameters.Add(New OleDbParameter("middle_name", CType(TextBox2.Text, String)))
        cmd.Parameters.Add(New OleDbParameter("last_name", CType(TextBox3.Text, String)))

        Try
            cmd.ExecuteNonQuery()
            cmd.Dispose()
            myConnection.Close()
            TextBox1.Clear()
            TextBox2.Clear()
            TextBox3.Clear()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
End Class