如何修复“？”附近的错误语法

Question

当我执行此代码时，我在 SQL 命令中遇到错误

'?' 附近的语法不正确

这是我的代码：

Dim command As New SqlCommand("SELECT [username], [password] FROM [stud_table] WHERE [username] = ?", connection)
command.Parameters.AddWithValue("username", Me.UsernameTextBox.Text)

Try
    connection.Open()

    Dim adapter As New SqlDataAdapter(command)

    Dim rec As SqlDataReader = command.ExecuteScalar()

    If rec.HasRows Then
        rec.Read()

        If Me.PasswordTextBox.Text.ToLower = rec.Item("password").ToString Then
            MsgBox("Login successful")
            Me.Hide()
            user_profile.Show()
        Else
            MsgBox("Login unsuccessful, Incorrect Password", MsgBoxStyle.OkOnly, "Invalid")
        End If
    Else
        MsgBox("Login unsuccessful, Invalid UserName", MsgBoxStyle.OkOnly, "Invalid")
    End If
    rec.Close()
Catch ex As OleDb.OleDbException
    MsgBox("Login unsuccessful,no connection", MsgBoxStyle.OkOnly, "Invalid")
Catch ex As Exception
    MessageBox.Show(ex.Message)
Finally
    connection.Close()
End Try

Answer 1

在查询中使用参数名称：

Dim command As New SqlCommand("SELECT [username],[password] FROM [stud_table] WHERE [username] = @username", connection)
        command.Parameters.AddWithValue("@username", SqlDbType.NVarChar) = Me.UsernameTextBox.Text