Question

请参阅以下代码：

Public Sub GetConnectionString(Dim strCon As String)
            Dim stringtochange As String = ConfigurationManager.ConnectionStrings("GeniedbConnection").ConnectionString 'line 2
            Dim configFile As System.Configuration.Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
            Dim connectionStringsSection As ConnectionStringsSection
            connectionStringsSection = CType(configFile.GetSection("GeniedbConnection"), ConnectionStringsSection)
            connectionStringsSection.ConnectionStrings("GeniedbConnection").ConnectionString = strCon 'Line 6
            configFile.Save()
        End Sub

我正在尝试更改app.config中的连接字符串。第2行返回当前连接字符串。第6行抛出异常：`“对象引用未设置为对象的实例。”这是为什么？

Answer 1

第2行

Dim stringtochange As String = ConfigurationManager.ConnectionStrings("GeniedbConnection").ConnectionString

与第6行不同

connectionStringsSection.ConnectionStrings("GeniedbConnection").ConnectionString = strCon

ConfigurationManager！= connectionStringsSection

其中任何一个都为空，connectionStringsSection，connectionStringsSection.ConnectionStrings("GeniedbConnection")

对象引用未设置为从代码更改app.config中的连接字符串的对象实例

1 个答案: