完整的添加，更新，删除操作 App.config 的类

Imports System.Configuration

Public Class MyExeConfig

	Private conf As Configuration

	Public Sub New()
		conf = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
	End Sub

	Public Sub Save()
		conf.Save(ConfigurationSaveMode.Modified)
		ConfigurationManager.RefreshSection("appSettings")
	End Sub

	Public Function getValue(ByVal sKey As String) As String
		If checkKey(sKey) Then
			Return conf.AppSettings.Settings.Item(sKey).Value
		Else
			Return String.Empty
		End If
	End Function

	Public Sub Add(ByVal sKey As String, ByVal sValue As String)
		conf.AppSettings.Settings.Add(sKey, sValue)
	End Sub

	Public Sub Remove(ByVal sKey As String)
		conf.AppSettings.Settings.Remove(sKey)
	End Sub

	Public Sub Update(ByVal sKey As String, ByVal sValue As String)
		If checkKey(sKey) Then
			conf.AppSettings.Settings.Item(sKey).Value = sValue
		End If
	End Sub

	Public Function checkKey(ByVal sKey As String) As Boolean
		Dim bFind As Boolean = False
		Dim keyarr As String() = conf.AppSettings.Settings.AllKeys
		For Each k As String In keyarr
			If 0 = String.Compare(k, sKey, StringComparison.Ordinal) Then
				bFind = True
				Exit For
			End If
		Next
		Return bFind
	End Function

End Class

使用前先系窗体启动先NEW一下，MyExeConfig.exe.Config会自动加内容

  <appSettings>
    <add key="iYouKey" value="4" />
  </appSettings>