[c#] 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?

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

I struggled with this for a while and finally figured it out on my own. I didn't find any help at the time, but wanted to share my approach. I have done this several times and used a different method than what is above. Not sure how robust it is, but it has worked for me.

Let's say you have a textbox named "txtName", a button named "btnSave" and you want to save the name so the next time you run your program the name you typed appears in that textbox.

1. Go to Project>Properties>Settings and create a setting -

• name = "Name"
• type = "string"
• scope = "user"
• value you can leave blank.

Save your settings file.

2. Go to your form where textbox and button exist. Double click your button and put this code in;

    //This tells your program to save the value you have to the properties file (app.config);
    //"Name" here is the name you used in your settings file above.
    Properties.Settings.Default.Name = txtName.txt;
    //This tells your program to make these settings permanent, otherwise they are only
    //saved for the current session
    Properties.Settings.Default.Save();

3. Go to your form_load function and add this in there;

    //This tells your program to load the setting you saved above to the textbox
    txtName.txt = Properties.Settings.Default.Name;

4. Debug your application and you should see the name you typed in.
5. Check your application debug directory and you should see a .config file named after your program. Open that with a text editor and you will see your settings.

Notes -

• "Name" refers to the actual name of the setting you created.
• Your program will take care of creating the actual XML file, you don't have to worry about it.

string filePath = System.IO.Path.GetFullPath("settings.app.config");

var map = new ExeConfigurationFileMap { ExeConfigFilename = filePath };
try
{
    // Open App.Config of executable
    Configuration config = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);

    // Add an Application Setting if not exist

        config.AppSettings.Settings.Add("key1", "value1");
        config.AppSettings.Settings.Add("key2", "value2");

    // Save the changes in App.config file.
    config.Save(ConfigurationSaveMode.Modified);

    // Force a reload of a changed section.
    ConfigurationManager.RefreshSection("appSettings");
}
catch (ConfigurationErrorsException ex)
{
    if (ex.BareMessage == "Root element is missing.")
    {
        File.Delete(filePath);
        return;
    }
    MessageBox.Show(ex.Message);
}

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");
}

For a .NET 4.0 console application, none of these worked for me. So I used the following 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");
}

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.

//if you want change
Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);
config.AppSettings.Settings[key].Value = value;

//if you want add
Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);
config.AppSettings.Settings.Add("key", value);

Yes you can - see ConfigurationManager

The ConfigurationManager class includes members that enable you to perform the following tasks:

• Read and write configuration files as a whole.

Learn to use the docs, they should be your first port-of call for a question like this.

Try the following code:

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

It worked for me :-)

Try the following:

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);            
config.AppSettings.Settings[key].Value = value;
config.Save();
ConfigurationManager.RefreshSection("appSettings");