I have following app.config. I would like save into ConnectionString key value - my text from serialized xml.
Private Shared strcon As String = New AppSettingsReader().GetValue("ConnectionString", GetType(System.String)).ToString()
    <?xml version="1.0" encoding="utf-8" ?>
    <configuration>
      <appSettings>
           <add key="ConnectionString" value=""/>  
      </appSettings>
        <system.diagnostics>
            <sources>
...
So far i got this code but i am receiving error: "Object reference not set to an instance of an object."
on the line: config.AppSettings.Settings("ConnectionString").Value = "myconn"
' Get the configuration file.
        Dim config As Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
        ' Update the setting.
        config.AppSettings.Settings("ConnectionString").Value = "myconn" 
        ' Save the configuration file.
        config.Save(ConfigurationSaveMode.Modified)
        ' Force a reload of the changed section.
        ConfigurationManager.RefreshSection("appSettings")
