mysql - 如何从类中调用模块？

Question

你看，我们的老师给了我们一些代码来学习，我计划使用它们来创建一个登录系统，但我不知道如何做。我对此相当陌生，并且渴望学习。我非常需要帮助。

Imports MySql.Data.MySqlClient

Module MySqlManager

    Public Function GetMySqlConnStr() As String
        Dim connStrBuilder As New MySqlConnectionStringBuilder

        With connStrBuilder
            .Server = "localhost"
            .UserID = "root"
            .Password = ""
            .Database = "bloodbank"
            .Port = 3306
        End With

        ''Returns the mysql connection string
        Return connStrBuilder.ConnectionString
    End Function


    ''' <summary>
    ''' Use ExecuteNonQuery for INSERT/UPDATE/DELETE query. Returns 0 if failed.
    ''' </summary>
    ''' <param name="commandText"></param>
    ''' <param name="parameters"></param>
    Public Function ExecuteNonQuery(ByVal commandText As String, ByVal ParamArray parameters As MySqlParameter()) As Integer
        Using conn As New MySqlConnection(GetMySqlConnStr)
            Using cmd As New MySqlCommand(commandText, conn)
                conn.Open()

                cmd.Prepare()
                cmd.CommandType = CommandType.Text
                If parameters IsNot Nothing Then
                    cmd.Parameters.AddRange(parameters)
                End If

                Return cmd.ExecuteNonQuery()

            End Using
        End Using
    End Function

    ''' <summary>
    ''' Use ExecuteScalar for querying a single value
    ''' </summary>
    ''' <param name="commandText"></param>
    ''' <param name="parameters"></param>
    Public Function ExecuteScalar(commandText As String, ParamArray parameters As MySqlParameter()) As Object
        Using conn As New MySqlConnection(GetMySqlConnStr)
            Using cmd As New MySqlCommand(commandText, conn)
                conn.Open()

                cmd.Prepare()
                cmd.CommandType = CommandType.Text
                If parameters IsNot Nothing Then
                    cmd.Parameters.AddRange(parameters)
                End If

                Return cmd.ExecuteScalar()
            End Using
        End Using
    End Function

    ''' <summary>
    ''' Use ExecuteReader when you are making an SQL call that will return a record set from a table.
    ''' </summary>
    ''' <param name="commandText"></param>
    ''' <param name="parameters"></param>
    Public Function ExecuteReader(ByVal commandText As String, ByVal ParamArray parameters As MySqlParameter()) As MySqlDataReader
        Dim conn As New MySqlConnection(GetMySqlConnStr)
        Using cmd As New MySqlCommand(commandText, conn)

            conn.Open()

            cmd.Prepare()
            cmd.CommandType = CommandType.Text

            If parameters IsNot Nothing Then
                cmd.Parameters.AddRange(parameters)
            End If

            Dim reader As MySqlDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)

            Return reader

        End Using

    End Function
End Module

Answer 1

Class SomClass
Dim stringValue as string = MySqlManager.GetMySqlConnStr()
End Class

module 和 class 之间的区别在于，当您可以时，您只能拥有 module 的一个实例。有多个类实例。