ConfigurationManager.AppSettings Property

public:
 static property System::Collections::Specialized::NameValueCollection ^ AppSettings { System::Collections::Specialized::NameValueCollection ^ get(); };

public static System.Collections.Specialized.NameValueCollection AppSettings { get; }

static member AppSettings : System.Collections.Specialized.NameValueCollection

Public Shared ReadOnly Property AppSettings As NameValueCollection

The contents of the AppSettingsSection object for the current application's default configuration.

The first example shows a simple console application that reads application settings, adds a new setting, and updates an existing setting.

using System;
using System.Configuration;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadAllSettings();
            ReadSetting("Setting1");
            ReadSetting("NotValid");
            AddUpdateAppSettings("NewSetting", "May 7, 2014");
            AddUpdateAppSettings("Setting1", "May 8, 2014");
            ReadAllSettings();
        }

        static void ReadAllSettings()
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;

                if (appSettings.Count == 0)
                {
                    Console.WriteLine("AppSettings is empty.");
                }
                else
                {
                    foreach (var key in appSettings.AllKeys)
                    {
                        Console.WriteLine("Key: {0} Value: {1}", key, appSettings[key]);
                    }
                }
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }

        static void ReadSetting(string key)
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                string result = appSettings[key] ?? "Not Found";
                Console.WriteLine(result);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }

        static void AddUpdateAppSettings(string key, string value)
        {
            try
            {
                var configFile = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                var settings = configFile.AppSettings.Settings;
                if (settings[key] == null)
                {
                    settings.Add(key, value);
                }
                else
                {
                    settings[key].Value = value;
                }
                configFile.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection(configFile.AppSettings.SectionInformation.Name);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error writing app settings");
            }
        }
    }
}

Imports System.Configuration
Module Module1

    Sub Main()
        ReadAllSettings()
        ReadSetting("Setting1")
        ReadSetting("NotValid")
        AddUpdateAppSettings("NewSetting", "May 7, 2014")
        AddUpdateAppSettings("Setting1", "May 8, 2014")
        ReadAllSettings()
    End Sub

    Sub ReadAllSettings()
        Try
            Dim appSettings = ConfigurationManager.AppSettings

            If appSettings.Count = 0 Then
                Console.WriteLine("AppSettings is empty.")
            Else
                For Each key As String In appSettings.AllKeys
                    Console.WriteLine("Key: {0} Value: {1}", key, appSettings(key))
                Next
            End If
        Catch e As ConfigurationErrorsException
            Console.WriteLine("Error reading app settings")
        End Try
    End Sub

    Sub ReadSetting(key As String)
        Try
            Dim appSettings = ConfigurationManager.AppSettings
            Dim result As String = appSettings(key)
            If IsNothing(result) Then
                result = "Not found"
            End If
            Console.WriteLine(result)
        Catch e As ConfigurationErrorsException
            Console.WriteLine("Error reading app settings")
        End Try
    End Sub

    Sub AddUpdateAppSettings(key As String, value As String)
        Try
            Dim configFile = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
            Dim settings = configFile.AppSettings.Settings
            If IsNothing(settings(key)) Then
                settings.Add(key, value)
            Else
                settings(key).Value = value
            End If
            configFile.Save(ConfigurationSaveMode.Modified)
            ConfigurationManager.RefreshSection(configFile.AppSettings.SectionInformation.Name)
        Catch e As ConfigurationErrorsException
            Console.WriteLine("Error writing app settings")
        End Try
    End Sub

End Module

An AppSettingsSection object contains the contents of the configuration file's appSettings section.

• AppSettingsSection
• NameValueCollection