VB.NET问题，插入到Access DB中，ExecutNonQuery未初始化

Question

我需要帮助来获取输入的信息并将其插入到简单的Access DB中。仅使用三个文本框，DB只有三列。当我选择写入数据库的按钮时，遇到一条消息，指出“ ExecuteNonQuery连接属性尚未初始化”。代码如下，在寻求帮助来确定查询未插入Access DB的问题。

If txtFirstNumber.Text = "" Or txtSecondNumber.Text = "" Then
        MsgBox("Please fill the details")
    Else
        Try
            Using conn = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Shawn\Desktop\Dave\CertificationCourse-AMU\ENTD461 - Advanced VB.Net\wk6\Week6ExerciseDB.accdb;")
                conn.Open()

                Dim sql As New OleDbCommand("INSERT INTO Mathops[FirstNumber],[SecondNumber],[Results] Values (@FirstNumber, @SecondNumber, @Results)")

                With sql.Parameters
                    .AddWithValue("@FirstNumber", txtFirstNumber.Text)
                    .AddWithValue("@SecondNumber", txtSecondNumber.Text)
                    .AddWithValue("@Result", txtResult.Text)
                End With
                sql.ExecuteNonQuery()

                MessageBox.Show("Week6ExerciseDB Successfully Updated", "INFO", MessageBoxButtons.OK, MessageBoxIcon.Information)

                sql.Dispose()
                conn.Close()

                txtFirstNumber.Text = ""
                txtSecondNumber.Text = ""
                txtResult.Text = ""
            End Using
        Catch ex As Exception
            MessageBox.Show(ex.Message, "ERROR12", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End If