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Modifying Web.Config During Installation

, 26 Jan 2006
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How to modify the Web.Config of a WebService during installation.


This application illustrates an installer that changes the values in a webservice's web.config file during setup, according to user entry. The application changes values of key values in the web.config file.


As web.config is a configuration file for ASP.NET applications or ASP.NET web service applications to store data, it can be modified by the user after application setup using Notepad or programmatically. Most programmers use web.config as it stored data that can be changed dynamically by the user.

  <add key="Name"  value="Keyvalue"/>

A user might have to open and change this file many times if a web application or service is moved from one server to another frequently, so in the installer I've enabled a facility for a user to change the values of attributes of his choice.

My example in this application changes the connection string used by a web service.

  <add key="Main.ConnectionString" 
               User ID=sa;Password=;

So in the installer, I change the key value by implementing the installer class in a webservice project.

Then in the installer class, I override the Install function:

public override void Install(IDictionary stateSaver)
    //You type here your own code
    base.Install (stateSaver);

To get data required to change the values in web.config from the user, I add in the setup project, a custom action:

I the change custom data property for it to:


[EDITA1], [EDITA2], [EDITA3], [EDITA4] are names of textboxes in the dialog added in the setup project interface.

You will notice the value here:


I've separated the parameters to the Installer class by a special letter (@) to split them later as Visual Studio concatenates all the parameters to the first parameter and empty others.

void FormateParamters()
    string strServer,strUser , strPassword ,strFolder;
    EventLog.WriteEntry("TNT", Context.Parameters["Server"]);






The previous function is to format the parameters by splitting them using the special character (@) so we can use them later for the connection string reconstruction function:

void CreateConnectionString()

    Assembly ass=Assembly.GetExecutingAssembly();
    EventLog.WriteEntry ("Web.Config", 

    Stream stmConfig=ass.GetManifestResourceStream(


    FileStream stmPhysical=new FileStream(
    StreamReader srConfig=new StreamReader(stmConfig);
    StreamWriter swConfig=new StreamWriter(stmPhysical);

    string strConfig=srConfig.ReadToEnd();
    strConfig=strConfig.Replace("server=(local);database" + 
              "=DatabaseName;User ID=sa;Password=;" + 

    swConfig.Close ();


The above function copies the web.config from the physical path and begins to replace the old key value with the new value.

Note: the local folder parameter must be the same path where the webservice is installed in. In this case, it is:



This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Amal ElHosseiny
Web Developer
Egypt Egypt
No Biography provided

Comments and Discussions

QuestionWeb.config edit Pinmemberkaushikpathak18-Oct-13 0:14 
Questionhow to show the existing values in the textboxes before installation? PinmemberPraveen Jeganathan22-Apr-13 0:58 
GeneralMy vote of 4 PinmemberKiweenJain11-Nov-12 21:32 
GeneralCreate Web Service Installer PinmemberMember 38889644-May-09 0:58 
GeneralGreat article! PinmemberThomas ST21-Apr-09 3:02 
GeneralPossible better way to acquire web.config path PinmemberBillyGoatGruff8-Apr-09 5:22 
GeneralRe: Possible better way to acquire web.config path [modified] PinmemberThomas ST21-Apr-09 2:57 
QuestionModifing the Project for the Installer??? PinmemberRicardo Casquete3-Feb-08 16:16 
Generalproblem in installation Pinmemberchinni10000719-Sep-07 18:56 
GeneralRe: problem in installation Pinmemberanand.lv16-Jan-09 2:26 
GeneralRe: Problems when comments in web.config &lt;!-- Some Comment --> PinmemberAmal ElHosseiny29-Mar-07 23:18 
GeneralRe: Problems when comments in web.config &amp;lt;!-- Some Comment --&gt; Pinmemberassadhf30-Mar-07 1:11 
GeneralSuggestion Pinmembersyemhusa21-Nov-06 23:42 
GeneralLocal folder-path Pinmemberedgecrush3r27-Sep-06 0:46 
Generalsorry ... broken download Pinmembermarquito_cuba27-Jul-06 6:18 
GeneralRe: sorry ... broken download PinmemberAmal ElHosseiny30-Jul-06 20:59 
GeneralUse of EventLog.WriteEntry In this article PinmemberAuldrin John Possa22-Feb-06 16:23 
GeneralRe: Use of EventLog.WriteEntry In this article PinmemberAmal ElHosseiny3-Mar-06 22:26 
GeneralVery useful Pinmembermosessaur13-Feb-06 3:05 
GeneralWeb Application Folder Pinmemberash75-Feb-06 23:57 
GeneralNice Job PinmemberBrent Finney2-Feb-06 8:16 
GeneralProblem Pinmemberash72-Feb-06 0:51 
GeneralRe: Problem PinmemberAmal ElHosseiny2-Feb-06 0:56 
GeneralRe: Problem Pinmemberash72-Feb-06 18:57 
GeneralRe: Problem PinmemberAmal ElHosseiny3-Feb-06 0:01 

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Article Copyright 2006 by Amal ElHosseiny
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