Write values in app.config file

can anyone please help me how can I set/store values in the app.config file using c#, is it possible at all?

Try the following code:

    Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);
    config.AppSettings.Settings.Add("YourKey", "YourValue");
    config.Save(ConfigurationSaveMode.Minimal);

It worked for me :-)

On Framework 4.5 the AppSettings.Settings["key"] part of ConfigurationManager is read only so I had to first Remove the key then Add it again using the following:

Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);

config.AppSettings.Settings.Remove("MySetting");
config.AppSettings.Settings.Add("MySetting", "some value");

config.Save(ConfigurationSaveMode.Modified);

Don't worry, you won't get an exception if you try to Remove a key that doesn't exist.

This post gives some good advice

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");
}

If you are using App.Config to store values in <add Key="" Value="" /> or CustomSections section use ConfigurationManager class, else use XMLDocument class.

For example:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="server" value="192.168.0.1\xxx"/>
    <add key="database" value="DataXXX"/>
    <add key="username" value="userX"/>
    <add key="password" value="passX"/>
  </appSettings>
</configuration>

You could use the code posted on CodeProject

As others mentioned, you can do this with ConfigurationManager.AppSettings.Settings. But: Using Settings[key] = value will not work if the key doesn't exist.
Using Settings.Add(key, value), if the key already exists, it will join the new value to its value(s) separated by a comma, something like <add key="myKey" value="value1, value2, value3" />

To avoid these unexpected results, you have to handle two scenario's

If entry with the given key exists? then update its value
if entry with the given key doesn't exist? then create new entry(key,value)

Code

public static void Set(string key, string value)
{
    var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

    var entry = config.AppSettings.Settings[key];
    if (entry == null)
        config.AppSettings.Settings.Add(key, value);
    else
        config.AppSettings.Settings[key].Value = value;

    config.Save(ConfigurationSaveMode.Modified);
}

For more info about the check entry == null, check this post.
Hope this will help someone.

Write values in app.config file

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