App.Config change value

Question

This is my App.Config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="lang" value="English"/>
  </appSettings>
</configuration>

With this code I make the change

lang = "Russian";
private void Main_FormClosing(object sender, FormClosingEventArgs e)
{
     System.Configuration.ConfigurationManager.AppSettings.Set("lang", lang);
}

But it not change. What I'm doing wrong?

Estrange

possible duplicate of Write values in app.config file – Ergo

Answer 1

You cannot use AppSettings static object for this. Try this

string appPath = System.IO.Path.GetDirectoryName(Reflection.Assembly.GetExecutingAssembly().Location);          
string configFile = System.IO.Path.Combine(appPath, "App.config");
ExeConfigurationFileMap configFileMap = new ExeConfigurationFileMap();         
configFileMap.ExeConfigFilename = configFile;          
System.Configuration.Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None);

config.AppSettings.Settings["YourThing"].Value = "New Value"; 
config.Save(); 

Olivann

But it restarts... I making the change on Form closing... When I run program again nothing change – Estrange

do you get any exceptions? Are you using WinForms? – Olivann

On my .Net (4.5) with Visual Studio 2013 Ultimate, I can have System.Configuration but no such object as System.Configuration.Configuration. – Spicebush

It throws NullReferenceException when setting the value. config.AppSettings.Settings count is zero though I have a key in my appSettings. I am on c# 4.5 – Emigration

@TechJerk Are you using app.config or web.config? – Olivann

Answer 2

AppSettings.Set does not persist the changes to your configuration file. It just changes it in memory. If you put a breakpoint on System.Configuration.ConfigurationManager.AppSettings.Set("lang", lang);, and add a watch for System.Configuration.ConfigurationManager.AppSettings[0] you will see it change from "English" to "Russian" when that line of code runs.

The following code (used in a console application) will persist the change.

class Program
{
    static void Main(string[] args)
    {
        UpdateSetting("lang", "Russian");
    }

    private static void UpdateSetting(string key, string value)
    {
        Configuration configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        configuration.AppSettings.Settings[key].Value = value;
        configuration.Save();

        ConfigurationManager.RefreshSection("appSettings");
    }
}

From this post: http://vbcity.com/forums/t/152772.aspx

One major point to note with the above is that if you are running this from the debugger (within Visual Studio) then the app.config file will be overwritten each time you build. The best way to test this is to build your application and then navigate to the output directory and launch your executable from there. Within the output directory you will also find a file named YourApplicationName.exe.config which is your configuration file. Open this in Notepad to see that the changes have in fact been saved.

Habitation

How I can make the change then? – Estrange

System.Configuration.ConfigurationManager.AppSettings[0] will not do nothing alone... Please fill the code – Estrange

So I must write System.Configuration.ConfigurationManager.AppSettings[0] = lang? Because that give me error – Estrange

I copied your code and run on VS 2012 c# 4.5 , it isn't working. I did check the bin/debug folder config file. It works only when I add the "configFileMap" as given in accepted answer – Emigration

It doesn't save permanently. When I debug I can see the value is changed but after complete execution, previous value is restored. – Emigration

For more robust code you could add a test if the key already exists: if (configuration.AppSettings.Settings[key] == null) configuration.AppSettings.Settings.Add(key, value); else configuration.AppSettings.Settings[key].Value = value; – Alemanni

Nice Major Point. – Rigidify

Answer 3

when use "ConfigurationUserLevel.None" your code is right run when you click in nameyourapp.exe in debug folder. .
but when your do developing app on visual stdio not right run!! because "vshost.exe" is run.

following parameter solve this problem : "Application.ExecutablePath"

try this : (Tested in VS 2012 Express For Desktop)

Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);
config.AppSettings.Settings["PortName"].Value = "com3";
config.Save(ConfigurationSaveMode.Minimal);

my english not good , i am sorry.

Primary

Answer 4

That worked for me in WPF application:

string configPath = Path.Combine(System.Environment.CurrentDirectory, "YourApplication.exe");
Configuration config = ConfigurationManager.OpenExeConfiguration(configPath);
config.AppSettings.Settings["currentLanguage"].Value = "En";
config.Save();

Erepsin

@jned29 feel free to upvote my answer, if it helps to you:). – Erepsin

Answer 5

    private static string GetSetting(string key)
    {
        return ConfigurationManager.AppSettings[key];
    }

    private static void SetSetting(string key, string value)
    {
        Configuration configuration =
            ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        configuration.AppSettings.Settings[key].Value = value;
        configuration.Save(ConfigurationSaveMode.Full, true);
        ConfigurationManager.RefreshSection("appSettings");
    }

Humberto

You may not want to save the config in ConfigurationSaveMode.Full. This will ad a ton of stuff to your app.config that you do not want. The rest is good. – Hoopoe

You may also want to combine with the Application.ExecutablePath option for calling OpenExeConfiguration, as mentioned in @Amin Ghaderi's answer – Colourable

Answer 6

In addition to the answer by fenix2222 (which worked for me) I had to modify the last line to:

config.Save(ConfigurationSaveMode.Modified);

Without this, the new value was still being written to the config file but the old value was retrieved when debugging.

Brotherly

Answer 7

For a .NET 4.0 console application, none of these worked for me. So I modified Kevn Aenmey's answer as below and it worked:

private static void UpdateSetting(string key, string value)
{
    Configuration configuration = ConfigurationManager.
        OpenExeConfiguration(Assembly.GetExecutingAssembly().Location);
    configuration.AppSettings.Settings[key].Value = value;
    configuration.Save();

    ConfigurationManager.RefreshSection("appSettings");
}

Only the first line is different, constructed upon the actual executing assembly.

Bobette

Answer 8

Thanks Jahmic for the answer. Worked properly for me.

another useful code snippet that read the values and return a string:

public static string ReadSetting(string key)
    {
        System.Configuration.Configuration cfg = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        System.Configuration.AppSettingsSection appSettings = (System.Configuration.AppSettingsSection)cfg.GetSection("appSettings");
        return appSettings.Settings[key].Value;

    }

Atalante

Answer 9

To update entries other than appsettings, simply use XmlDocument.

public static void UpdateAppConfig(string tagName, string attributeName, string value)
{
    var doc = new XmlDocument();
    doc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
    var tags = doc.GetElementsByTagName(tagName);
    foreach (XmlNode item in tags)
    {
        var attribute = item.Attributes[attributeName];
        if (!ReferenceEquals(null, attribute))
            attribute.Value = value;
    }
    doc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
}

This is how you call it:

Utility.UpdateAppConfig("endpoint", "address", "http://localhost:19092/NotificationSvc/Notification.svc");

Utility.UpdateAppConfig("network", "host", "abc.com.au");

This method can be improved to cater for appSettings values as well.

Anaximenes