Configuration Transformation (1) - Web.Config

This series of articles shows how to automate the process of changing the config file when deploying an App to different destination environments.

This article shows how to automate the process of changing the Web.config file when deploying an ASP.NET Web App to different destination environments.

Introduction

The content of this article:

  • Transform File
  • Web.Config Transformation
  • Create Custom Web.Config Transformation

Transform File

A transform file is an XML file that specifies how the Web.config file should be changed when it is deployed. Transformation actions are specified by using XML attributes that are defined in the XML-Document-Transform namespace, which is mapped to the xdt prefix.

The XML-Document-Transform namespace defines two attributes:

  • Locator: specifies the Web.config element or set of elements that you want to change in some way.
  • Transform: specifies what you want to do to the elements that the Locator attribute finds.

The following example shows the contents of a transform file that changes a connection string and replaces the customErrors element:

<?xml version="1.0"?>
<configuration xmlns:xdt="https://schemas.microsoft.com/XML-Document-Transform">
  <connectionStrings>
    <add name="MyDB" 
      connectionString="value for the deployed Web.config file" 
      xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
  </connectionStrings>
  <system.web>
    <customErrors defaultRedirect="GenericError.htm"
      mode="RemoteOnly" xdt:Transform="Replace">
      <error statusCode="500" redirect="InternalError.htm"/>
    </customErrors>
  </system.web>
</configuration>

Web.Config Transformation

Most applications have settings in the Web.config file that must be different when the application is deployed. Automating the process of making these changes keeps you from having to do them manually every time you deploy, which would be tedious and error-prone.

There are two ways to automate the process of changing Web.config file settings: 

Web.config transformation file contains XML markup that specifies how to change the Web.config file when it is deployed. You can specify different changes for specific build configurations and for specific publish profiles.

The default build configurations are Debug and Release,

Configuration Transformation (1): Web.Config

and you can create custom build configurations. A publish profile typically corresponds to a destination environment. 

Create Custom Web.Config Transformation

Configuration Manager:

We use a configuration manager to create a custom Web.Config transform. We have several ways to open a configuration manager:

From Visual studio Build Tab.

Configuration Transformation (1): Web.Config

Right Click solution.

Configuration Transformation (1): Web.Config

From environment windows.

Configuration Transformation (1): Web.Config

From CPU windows.

Configuration Transformation (1): Web.Config

Add New Project Configuration

We can either in solution level.

Configuration Transformation (1): Web.Config

Or project level.

Configuration Transformation (1): Web.Config

Add New, make sure that the "Copy settings from:" is <Empty> and the "Create new project configurations" is checked.

Configuration Transformation (1): Web.Config

Added for Project MVC_ActionFilter.

Configuration Transformation (1): Web.Config

Newly created configuration is qac at both project level and solution level, while other projects are the same as previously:

Configuration Transformation (1): Web.Config

After adding the configuration, check the solution file, we can see the "qac" is added:

Configuration Transformation (1): Web.Config

In the project file, it is added too:

Configuration Transformation (1): Web.Config

Add config transform file

At this point, however, we do not see the configuration transform file added. Let us do it by right Click web.config file.

Configuration Transformation (1): Web.Config

Then we get the configuration transform file, web.qac.config, added:

Configuration Transformation (1): Web.Config

like this:

<?xml version="1.0" encoding="utf-8"?>

<!-- For more information on using web.config transformation visit https://go.microsoft.com/fwlink/?LinkId=125889 -->

<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <!--
    In the example below, the "SetAttributes" transform will change the value of 
    "connectionString" to use "ReleaseSQLServer" only when the "Match" locator 
    finds an attribute "name" that has a value of "MyDB".
    
    <connectionStrings>
      <add name="MyDB" 
        connectionString="Data Source=ReleaseSQLServer;Initial Catalog=MyReleaseDB;Integrated Security=True" 
        xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
    </connectionStrings>
  -->
  <system.web>
    <compilation xdt:Transform="RemoveAttributes(debug)" />
    <!--
      In the example below, the "Replace" transform will replace the entire 
      <customErrors> section of your web.config file.
      Note that because there is only one customErrors section under the 
      <system.web> node, there is no need to use the "xdt:Locator" attribute.
      
      <customErrors defaultRedirect="GenericError.htm"
        mode="RemoteOnly" xdt:Transform="Replace">
        <error statusCode="500" redirect="InternalError.htm"/>
      </customErrors>
    -->
  </system.web>
</configuration>

Preview transform

Configuration Transformation (1): Web.Config

We can see, the debug mode is disabled.

Configuration Transformation (1): Web.Config

by the code.

<compilation xdt:Transform="RemoveAttributes(debug)" />

Config for compiling

Use Configuration Manager, we can manage the compiling processes.  For example, we can set dev only with one project as below, then each time when we build, it will only build one project if we choose dev, which can save a lot of time for us. 

Configuration Transformation (1): Web.Config

References


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