Update app.config key value at run time in WPF

In this article, I am going to show how we can update a key value in app.config file in WPF. For this add reference of System.Configuration in your application.

Suppose we have a key in our app.config file like this:

Image 1.

At run time we will change "Country" Key Value.

This is my XAML code

<Window x:Class="UpdateAppConfigValueInWPF.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Height="350" Width="525" Title="Update App.config value in WPF">

    <Grid>

        <Button Content="Update" Click="Button_Click" Height="20" Width="70" Margin="205,77,228,214"></Button>

        <TextBox Height="23" HorizontalAlignment="Left" Margin="184,34,0,0" Name="textBoxCountry" VerticalAlignment="Top" Width="120" />

        <TextBlock Height="23" HorizontalAlignment="Left" Margin="79,34,0,0" Name="textBlock1" Text="New Value for Key" VerticalAlignment="Top" Width="99" />

    </Grid>

</Window>

 

This is my XAML.CS code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.Configuration;

using System.Xml;

 

namespace UpdateAppConfigValueInWPF

{

    /// <summary>

    /// Interaction logic for MainWindow.xaml

    /// </summary>

    public partial class MainWindow : Window

    {

        public MainWindow()

        {

            InitializeComponent();          

        }

 

        private void Button_Click(object sender, RoutedEventArgs e)

        {

            if (!string.IsNullOrEmpty(textBoxCountry.Text))

            {

                UpdateConfigKey("Country", textBoxCountry.Text);

                textBoxCountry.Text = string.Empty;

            }

            else

                MessageBox.Show("Please type some value.");

        }

        public void UpdateConfigKey(string strKey, string newValue)

        {

            XmlDocument xmlDoc = new XmlDocument();

            xmlDoc.Load(AppDomain.CurrentDomain.BaseDirectory + "..\\..\\App1.config");

 

            if (!ConfigKeyExists(strKey))

            {

                throw new ArgumentNullException("Key", "<" + strKey + "> not find in the configuration.");

            }

            XmlNode appSettingsNode = xmlDoc.SelectSingleNode("configuration/appSettings");

 

            foreach (XmlNode childNode in appSettingsNode)

            {

                if (childNode.Attributes["key"].Value == strKey)

                    childNode.Attributes["value"].Value = newValue;

            }

            xmlDoc.Save(AppDomain.CurrentDomain.BaseDirectory + "..\\..\\App1.config");

            xmlDoc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);

            MessageBox.Show("Key Upated Successfullly");

        } 

        public bool ConfigKeyExists(string strKey)

        {

            XmlDocument xmlDoc = new XmlDocument();

            xmlDoc.Load(AppDomain.CurrentDomain.BaseDirectory + "..\\..\\App1.config");

 

            XmlNode appSettingsNode = xmlDoc.SelectSingleNode("configuration/appSettings");

 

            foreach (XmlNode childNode in appSettingsNode)

            {

                if (childNode.Attributes["key"].Value == strKey)

                    return true;

            }

            return false;

        }

    }

} 

 

When I run the application it will ask for new value of key as shown below:

Image 2.

Now if we see App.config key then it is already been updated.

Image 3.