如何处理整个项目中的数据库连接

Question

我在模块中创建了一个函数来连接到 windows 应用程序的数据库

Imports System.Data.SqlClient
Module mod_main
Public Function connectDB() As SqlConnection
        Dim Connection As New SqlConnection
        Try
            If Connection.State = ConnectionState.Open Then
                Connection.Close()
            End If
            If IntegratedSecurity Then
                Connection.ConnectionString = "Data Source = " & server & ";Initial Catalog = " & db & ";Connection TimeOut =0;Integrated Security=True"
            Else
                Connection.ConnectionString = "Data Source = " & server & ";Initial Catalog = " & db & ";Connection TimeOut =0;User ID='" & usr & "';Password='" & pwd & "'"
            End If
            Connection.Open()
            Return Connection
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Function
End Module

我有很多功能，并且类使用了过多的数据库活动，因此我使用了上述连接 function.For 示例：

 Public Sub FillComboBox(ByVal ComboBox As C1.Win.C1List.C1Combo, ByVal Query As String, ByVal DisplayMember As String, ByVal ValueMember As String)
        Dim SourceDataSet As New DataSet
        Dim adapter As New SqlDataAdapter(Query, connectDB) /*Assigning connection here */
        adapter.Fill(SourceDataSet)
        ComboBox.DataSource = SourceDataSet.Tables(0)
        ComboBox.ColumnHeaders = False
        ComboBox.ColumnWidth = 0
        ComboBox.ExtendRightColumn = True
        ComboBox.DisplayMember = DisplayMember
        ComboBox.ValueMember = ValueMember
    End Sub

由于我是编程初学者，所以我的问题是，这是处理数据库连接的正确方法吗？

Answer 1

我建议您进行以下更改：

将 Connection 设为 public 以获得全球可访问性
在 config file 中保存连接字符串并从那里访问它
不需要关闭和重新打开连接只有在没有可用连接时才打开连接

In your case all time it creates a new connection when the function is invoked since you are declaring and initializing connection inside the function. so checking connection state is meaning less:

因此您的函数如下所示：

public Connection As New SqlConnection
Public Function connectDB() As SqlConnection
      Try
            Dim Constr As String =""
            If IntegratedSecurity Then
               Constr = ConfigurationManager.AppSetting("IconnectionString")
            Else
               Constr  = ConfigurationManager.AppSetting("connectionString")
            End If
            If Connection Is Nothing Then
                Connection = New SqlConnection(Constr)
            End If
            If Connection.State <> ConnectionState.Open Then
              Connection.Open()
            End If           
            Return Connection
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
End Function

如何处理整个项目中的数据库连接

How to handle database connectivity in entire project

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database-connection