VB.NET在使用中的应用

我可以做：

using connection
myDt1 = sqlSelect(connection, sql)
myDt2 = sqlSelect(connection, sql)
end using

使用SQLSelect：

Public Shared Function SQLSelect(ByVal provider As SqlConnection, ByVal strSQL As String, ByVal ParamArray params() As SqlParameter) As DataTable
Using connection = provider

SQLSelect = New DataTable

Dim dtReader As SqlDataReader
Dim command As SqlCommand = CreateSQLCommand(provider, strSQL,  params)

Try
    connection.Open()
    dtReader = command.ExecuteReader()
    SQLSelect.Load(dtReader)
    dtReader.Close()
Catch ex As Exception
    SQLSelect = Nothing
Finally
    'If connection.State = ConnectionState.Open Then
    '    connection.Close()
    'End If
    command.Dispose()
End Try

End Using '<--- Here drop connection
Return SQLSelect

公共共享函数SQLSelect（ByVal提供程序作为SqlConnection，ByVal strSQL作为String，ByVal paramary params（）作为SqlParameter）作为DataTable
使用connection=provider
SQLSelect=新数据表
将dtReader设置为SqlDataReader
Dim命令作为SqlCommand=CreateSQLCommand（提供程序、strSQL、参数）
尝试
connection.Open（）
dtReader=command.ExecuteReader（）
SQLSelect.Load（dtReader）
dtReader.Close（）
特例
SQLSelect=Nothing
最后
'如果connection.State=ConnectionState.Open，则
'连接。关闭（）
"完"
command.Dispose（）命令
结束尝试
使用“结束只需使用如下DAL模式：

Public Class DataAccessLayer
    'Implements IDataAccessLayer

    #Region "Members"

    Private ReadOnly connectionString As String
    Private ReadOnly configuration As IConfiguration
    Private ReadOnly exceptionHandler As IExceptionHandler

    #End Region

    #Region "Constructors"
    Public Sub New()
        Me.New(New Configuration(), New ExceptionHandler())
    End Sub

    Public Sub New(configuration As IConfiguration, exceptionHandler As IExceptionHandler)
        ' You can just pass in a ConnectionString, instead of my IConfiguration
        connectionString = configuration.GetDefaultConnectionString()
        'Me.exceptionHandler = exceptionHandler
    End Sub

    #End Region

    #Region "Opening and Closing Connection"

    Public Function GetConnection() As SqlConnection
        Dim conn = New SqlConnection(connectionString)
        Try
            conn.Open()
        Catch ex As SqlException
            'exceptionHandler.LogExceptions(ex, Nothing)
        Catch ex As Exception
            'exceptionHandler.LogExceptions(ex, Nothing)
        End Try
        Return conn
    End Function

    #End Region

    #Region "Stored Procedure Calls"

    Public Function TestConnection() As Boolean
        Try
            Dim conn = New SqlConnection(connectionString)
            conn.Open()
            conn.Close()
        Catch
            Return False
        End Try
        Return True
    End Function

    Public Function CallAStoredProcExample() As Boolean
        Dim codeObject As CodeObject = Nothing
        Try
            Using conn = Me.GetConnection()
                Using sqlCommand = New SqlCommand("sp_GetCodeByCodeID", conn)
                    sqlCommand.CommandType = CommandType.StoredProcedure
                    sqlCommand.Parameters.AddWithValue("@CodeId", 1)

                    Using dr = sqlCommand.ExecuteReader()
                        While dr.Read()
                            codeObject = New CodeObject(dr, True)
                        End While
                    End Using
                End Using
            End Using
        Catch ex As Exception
            Return False
        End Try
        Return True
    End Function
End Class


呼叫代码：

Dim DAL = New DataAccessLayer(yourConnectionString, Nothing)
DAL.CallAStoredProcExample()

您正在SqlSelect中关闭连接。。使用的全部目的是为您关闭和处理连接。我忘记了注释这两行，在en Using end添加drop connection，这真的很奇怪，因为参数是ByVal，不是吗？如果我每次都传递连接字符串而不是sqlconnection是否更好？您最好使用~connection.Open（）~out-SqlSelect并传递SqlSelect一个打开的连接。如果我在不同的类中有3个函数：-Main（）->调用例如ListAllData（）-
ListAllData->executesqlselect（sqlconnection，parameters），那么还要从SqlSelectLast问题中删除Using和EndUsing->哪个打开连接并使用SQLSelect执行最后一个类中的查询？
----
SQLSelect->which execute
正确且良好吗？