How to add or remove appsettings key/value pair in the web.config of a SharePoint web application programmatically

To add or remove an appsettings key/value pair in the web.config of a SharePoint web application, you have use the Add or Remove methods of the WebConfigModifications property of an instance of the SPWebApplication class. These two methods take a SPWebConfigModification object as parameter.

I build a class (WebConfigManagement) containing static methods to help you to add or remove appsettings key/value pair:

using System;

using System.Reflection;

using Microsoft.SharePoint.Administration;

namespace SharePointLiveForMe.SharePoint.Administration

{

    /// <summary>

    /// This class allows to add or remove entries in web.config.

    /// </summary>

    public class WebConfigManagement

    {

        /// <summary>

        /// This methods allows to add a key/value pair in the AppSettings section.

        /// </summary>

        /// <param name="Key">Name of the key</param>

        /// <param name="Value">Value</param>

        /// <param name="webApp">Web application</param>

        public static void AddAppSettingsKeyValue(string key, string value, SPWebApplication webApp)

        {

            if (!string.IsNullOrEmpty(key) && !string.IsNullOrEmpty(value) && webApp != null)

            {

                SPWebConfigModification modification = GetModification(key, value);

                if (!webApp.WebConfigModifications.Contains(modification))

                {

                    webApp.WebConfigModifications.Add(modification);

                    webApp.Farm.Services.GetValue<SPWebService>().ApplyWebConfigModifications();

                    webApp.Update();

                }

            }

            else

                throw new ArgumentNullException();

        }

        /// <summary>

        /// This methods allows to remove a key/value pair in the AppSettings section.

        /// </summary>

        /// <param name="key">Name of the key</param>

        /// <param name="value">Value</param>

        /// <param name="webApp">Web application</param>

        public static void RemoveAppSettingsKeyValue(string key, string value, SPWebApplication webApp)

        {

            if (!string.IsNullOrEmpty(key) && !string.IsNullOrEmpty(value) && webApp != null)

            {

                SPWebConfigModification modification = GetModification(key, value);

                if(webApp.WebConfigModifications.Contains(modification))

                {

                    webApp.WebConfigModifications.Remove(modification);

                    webApp.Farm.Services.GetValue<SPWebService>().ApplyWebConfigModifications();

                    webApp.Update();

                }

            }

            else

                throw new ArgumentNullException();

        }

        /// <summary>

        /// This method allows to build an SPWebConfigModification object.

        /// </summary>

        /// <param name="key">Name of the key</param>

        /// <param name="value">Value</param>

        /// <returns></returns>

        private static SPWebConfigModification GetModification(string key, string value)

        {

            if (!string.IsNullOrEmpty(key) && !string.IsNullOrEmpty(value))

            {

                SPWebConfigModification modification = new SPWebConfigModification();

                modification.Name = string.Format(@"add[@key=""{0}""]", key);

                modification.Path = "configuration/appSettings";

                modification.Value = string.Format(@"<add key=""{0}"" value=""{1}"" />", key, value);

                modification.Owner = Assembly.GetExecutingAssembly().FullName;

                modification.Sequence = 0;

                modification.Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode;

                return modification;

            }

            else

                throw new ArgumentNullException();

        }

    }

}

Hereunder is a little console application to show how to use the WebConfigManagement class:

using System;

using Microsoft.SharePoint.Administration;

using SharePointLiveForMe.SharePoint.Administration;

namespace Test.SharePointLiveForMe.SharePoint.Administration

{

    class Program

    {

        static void Main(string[] args)

        {

            SPFarm farm = SPFarm.Local;

            SPWebService service = farm.Services.GetValue<SPWebService>("");

            SPWebApplication myWebApplication = null;

            foreach (SPWebApplication webApplication in service.WebApplications)

            {

                if (webApplication.DisplayName == "My Web Application")

                    myWebApplication = webApplication;

            }

            Console.WriteLine("Write AppSettings Key/Value");

            WebConfigManagement.AddAppSettingsKeyValue("IsCool", "true", myWebApplication);

            Console.ReadLine();

            Console.WriteLine("Remove AppSettings Key/Value");

            WebConfigManagement.RemoveAppSettingsKeyValue("IsCool", "true", myWebApplication);

            Console.ReadLine();

        }

    }