mysql - App.config MySQL VB.Net 上有 2 个或更多 ConnectionString

Question

我得到了一个可以从 VB.Net 项目中的 App.Config 返回 ConnectionString 的代码。我的问题是我是否调用 online1 或 offline2 ，offline2 值正在被调用或更可能是默认值。

我想获取基于GetConnectionString([ConnectionString Name])的连接字符串

Public Shared Function GetConnectionString(ByVal strConnection As String) As String
    'Declare a string to hold the connection string
    Dim sReturn As New String(" ")
    Dim connections As ConnectionStringSettingsCollection = ConfigurationManager.ConnectionStrings
    'Check to see if they provided a connection string name
    If Not String.IsNullOrEmpty(strConnection) Then
        For Each connection As ConnectionStringSettings In connections
            If connection.Name = strConnection Then
                'Retrieve the connection string fromt he app.config
                sReturn = connection.ConnectionString
            Else
                'Since they didnt provide the name of the connection string
                'just grab the default on from app.config
                sReturn = connection.ConnectionString
            End If
        Next
    End If
    Return sReturn
End Function

应用程序配置

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <connectionStrings>
    <add name="online1" connectionString="SERVER=127.0.0.1; DATABASE=lto_db; UID=root; PASSWORD=;" providerName="MySql.Data.MySqlClient" />
    <add name="offline2" connectionString="SERVER=localhost; DATABASE=lto_db; UID=root; PASSWORD=;" providerName="MySql.Data.MySqlClient" />
  </connectionStrings>

</configuration>

Answer 1

只需使用:

Public Shared Function GetConnectionString(ByVal name As String) As String
    Dim connStrings = System.Configuration.ConfigurationManager.ConnectionStrings
    If String.IsNullOrEmpty(name) Then
        If connStrings.Count > 0 Then
            Return connStrings(0).ConnectionString
        Else
            Throw New Exception("No default connection string")
        End If
    Else
        Dim conn = connStrings(name)
        If conn Is Nothing Then Throw New Exception("No connection string named " & name)
        Return conn.ConnectionString
    End If
End Function

如果您还没有 System.Configuration 的引用，则需要引用

您的代码的问题是，如果连接名称为 null 或空，您甚至不执行循环，也不返回默认值(您只返回“”)。如果他们确实指定了一个名称并且它不是第一个，那么您将返回默认值并退出，即使有更多连接需要检查。