如何最小化变量的重复声明. [英] how to minimize repeat declaration of variable.

问题描述

在下面的代码中，我有两种不同的形式和一个类，我正在使用该类来建立和释放与数据库的连接.
我的问题如下:
1)如何最小化cn变量声明.
2)如何最小化cmd和其他变量声明(不是很需要，但是如果可能的话)

Here in following code i have two different forms and one class that class i am using for establish and release connection with database.
My questions are as follows:
1) how can i minimized cn variable declaration.
2) how to minimized cmd and other variable declaration(not very much needed but if possible)

'first class coding>
Imports System.Data.SqlClient
Public Class FrontDesk_approval_form
    Dim cn As Class1 = Class1.getInstance

    Dim cmd As SqlCommand
    Dim dr As SqlDataReader
    Dim da As SqlDataAdapter
    Dim ds, ds1 As New DataSet
    Dim str As String
    Dim temp_rowNo As String
    Dim temp_No As Integer
    Dim frm As New FrontDesk_approval_sub_form
    Public which_form As String = ""
   
    Private Sub bt_select_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bt_select.Click

        str = "select * from Asset_Service_Master where CaseId=@ temp_No "
        cmd = New SqlCommand(str, cn.getConnection())
        cmd.Parameters.Add(New SqlParameter("@temp_No",temp_No)

        dr = cmd.ExecuteReader()

        If dr.Read Then
            frm.tb_caseid.Text = dr.Item("CaseId")
            frm.temp_asset = dr.Item("Assets")
            frm.temp_brandname = dr.Item("BrandName")
            frm.temp_asset_type = dr.Item("AssetTypes")
            frm.temp_modelno = dr.Item("ModleNo")
            frm.temp_SerialNo = dr.Item("SerialNo")
            frm.temp_service_charge = dr.Item("ServiceCharge")
            frm.temp_service_Tex = dr.Item("ServiceTex")
            frm.which_form = which_form
            Me.Hide()
            frm.ShowDialog()

            Me.Dispose()
            Me.Close()
        End If
        cn.closingConnection()
 End Sub
end class

二级编码:

second class coding:

Imports System.Data.SqlClient
Public Class Front_Main

    Public maintain_user_name As String = ""
    Public maintain_password As String = ""
    Public maintain_department As String = ""

    Dim cmd As SqlCommand
    Dim dr As SqlDataReader
    Dim da As SqlDataAdapter
    Dim ds, ds1 As New DataSet
    Dim str As String
    Dim cn As Class1 = Class1.getInstance
    

    Private Sub bt_NewCaseId_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bt_NewCaseId.Click
        Dim f1 As New Front_New_Case
        f1.ShowDialog()
    End Sub

    Private Sub MainFormFrontDesk_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Activated


        str = "select Count(*)  from Asset_Service_Master where CaseStatus=  @temp "
        cmd = New SqlCommand(str, cn.getConnection())
        cmd.Parameters.Add(New SqlParameter("@temp", "pending for client approval"))

        tb_PendingForClientApproval.Text = cmd.ExecuteScalar().ToString

        str = "select count(*)  from Asset_Service_Master where CallClosed= @tp  AND BillingComplete=@tmp   "
        cmd = New SqlCommand(str, cn.getConnection())


        cmd.Parameters.Add(New SqlParameter("@tp", "yes"))
        cmd.Parameters.Add(New SqlParameter("@tmp", ""))

        tb_CalledClosed.Text = cmd.ExecuteScalar().ToString

        cn.closingConnection()

    End Sub

类编码为:

Class coding is:

Imports System.Data.SqlClient

Public Class Class1
    Private objcon As SqlConnection
    Private Shared inst As Class1

    Public Shared Function getInstance() As Class1
        'the following code identify that connection object having null or reference

        If inst Is Nothing Then
            inst = New Class1

        End If
        Return inst

    End Function

    Public Function getConnection() As SqlConnection
        'the following code identify that connection object having null or reference

        If objcon Is Nothing Then
            objcon = New SqlConnection("Data Source=.\sqlexpress;Initial Catalog=PROJ;Integrated Security=True")
            objcon.Open()
        End If
        If objcon.State = ConnectionState.Broken Or objcon.State = ConnectionState.Closed Then

            objcon.Open()

        End If
        Return objcon
    End Function

    Public Sub closingConnection()
        If objcon.State <> ConnectionState.Broken Then

            objcon.Close()

        End If
    End Sub

End Class

End Class

推荐答案

当我们已经实现并测试了代码后，为什么还要编写重复的代码.

您可以使用 SQLHelper类 [

Hi,

Why to write repeated code, when we have already implemented and tested code with us.

You can use SQLHelper class[^] to create your connection and execute your command. This class will handle everything for you.

Now you need to concentrate on other features.

Best luck.

这篇关于如何最小化变量的重复声明.的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！