The ConfigurationManager class provides a convenient way to manage application settings and connection strings in .NET applications.

Namespace and Assembly

• Namespace: System.Configuration
• Assembly: System.Configuration (in System.Configuration.dll)

Working with Application Settigns

To use ConfigurationManager, add a referecne to the System.Configuration assembly in your project. Application key-value pairs are typically stored in App.config (for desktop apps) or Web.config (for web apps).

Reading, Addding, and Updating Settings

The following example demonstrates common operations: listing all settings, reading a specific key, and adding or updating a value.

using System;
using System.Configuration;

namespace ConfigTool
{
    class Program
    {
        static void Main(string[] args)
        {
            EnumerateSettings();
            FetchSetting("Setting1");
            FetchSetting("InvalidKey");
            WriteOrReplaceSetting("NewSetting", "2024-07-10");
            WriteOrReplaceSetting("Setting1", "2024-07-11");
            EnumerateSettings();
        }

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

                if (appSettings.Count == 0)
                {
                    Console.WriteLine("No application settings found.");
                }
                else
                {
                    foreach (var key in appSettings.AllKeys)
                    {
                        Console.WriteLine("Key: {0} | Value: {1}", key, appSettings[key]);
                    }
                }
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Failed to read settings.");
            }
        }

        static void FetchSetting(string key)
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                string value = appSettings[key] ?? "Not Present";
                Console.WriteLine(value);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error accessing settings.");
            }
        }

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

Example App.config content:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <appSettings>
    <add key="Setting1" value="May 5, 2014"/>
    <add key="Setting2" value="May 6, 2014"/>
  </appSettings>
</configuration>

Using Connection Strings

Connection strings are defined in a dedicated <connectionStrings> section. The example below reads a connection string and queries a database.

using System;
using System.Configuration;
using System.Data.SqlClient;

namespace DataAccess
{
    class Program
    {
        static void Main(string[] args)
        {
            LoadProductList();
        }

        static void LoadProductList()
        {
            var connString = ConfigurationManager.ConnectionStrings["WingtipToys"].ConnectionString;
            string sql = "SELECT Id, ProductName FROM dbo.Products;";

            using (var conn = new SqlConnection(connString))
            {
                var cmd = new SqlCommand(sql, conn);
                conn.Open();
                using (var rdr = cmd.ExecuteReader())
                {
                    while (rdr.Read())
                    {
                        Console.WriteLine(String.Format("{0}, {1}", rdr[0], rdr[1]));
                    }
                }
            }
        }
    }
}

Corresponding App.config section:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
    <connectionStrings>
        <add name="WingtipToys" connectionString="Data Source=(LocalDB)\v11.0;Initial Catalog=WingtipToys;Integrated Security=True;Pooling=False" />
    </connectionStrings>
</configuration>