Modifying app.config File

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Introduction

This article will help you to change the <appSettings> values when you are deploying the application for the first time. At the time of application installation, we need to set application configuration parameters at the first time only. For example: When we change our database to another server, we can change Database Server Configuration Information into application Configuration file. At that time, we need to again modify the app.Config file by using our user Interface.

Background

The main purpose of this article is to Configure the application Configuration Settings. When we are Installing Windows Application, we have to update the app.Config file according to our requirements.

Using the Code

Here I have created a class that will help you to change the appSettings value. For that, you have to use this function with two parameters UpdateAppSettings().

You can call this function:

AppConfigFileSettings.UpdateAppSettings("DBServerName", txtNewKeyvalue.text)

You can update appSettings in this way:

// Class Name: AppConfigFileSettings
// Purpose: To Change appSettings Values

Imports System.Configuration
Imports System.Xml
''' <summary>
''' AppConfigFileSettings: This class is used to Change the 
''' AppConfigs Parameters at runtime through User Interface
''' </summary>
''' <remarks></remarks>
Public Class AppConfigFileSettings
    ''' <summary>
    ''' UpdateAppSettings: It will update the app.Config file AppConfig key values
    ''' </summary>
    ''' <param name="KeyName">AppConfigs KeyName</param>
    ''' <param name="KeyValue">AppConfigs KeyValue</param>
    ''' <remarks></remarks>
    Public Shared Sub UpdateAppSettings_
        (ByVal KeyName As String, ByVal KeyValue As String)
    '  AppDomain.CurrentDomain.SetupInformation.ConfigurationFile 
    ' This will get the app.config file path from Current application Domain
        Dim XmlDoc As New XmlDocument()
    ' Load XML Document
       XmlDoc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile)
    ' Navigate Each XML Element of app.Config file
        For Each xElement As XmlElement In XmlDoc.DocumentElement
            If xElement.Name = "appSettings" Then
                ' Loop each node of appSettings Element 
                ' xNode.Attributes(0).Value , Mean First Attributes of Node , 
                ' KeyName Portion
                ' xNode.Attributes(1).Value , Mean Second Attributes of Node,
                ' KeyValue Portion
                 For Each xNode As XmlNode In xElement.ChildNodes
                    If xNode.Attributes(0).Value = KeyName Then
                        xNode.Attributes(1).Value = KeyValue
                    End If
                Next
            End If
        Next
        ' Save app.config file
        XmlDoc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile)
    End Sub
End Class 
app.config File  
<configuration>
  <appSettings>
     <add key="DBServerName" value="Localhost"></add>
     <add key="DatabaseName" value="TestDB"></add>
     <add key="DatabaseUserID" value="sa"></add>
     <add key="DatabasePwd" value="sa"></add>
  </appSettings>
</configuration>

Points of Interest

1. Once you run this application to change the appSettings value, it will not affect an application until you Exit the application and run it again.
2. This article shows how to modify the app.config file. But how does this code help other users? - That depends on user requirements and your point of view.