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A powerful way to use the preprocessor is to substitute properties into placeholders in your XML file. Properties can be defined in an external XML file or passed on the command line.

For example if you have an application setting that contains the name of a remote server, but the name of that server changes from environment to environment, you may want to mark-up your XML like this:


    <!-- #ifdef _xml_preprocess -->
    <!-- <add key="server" value="${remoteserver}"/> -->
    <!-- #else -->
    <add key="server" value="developmentserver1"/>
    <!-- #endif -->

When the XML preprocessor is processes this file it will remove the comments from the body of the "ifdef" branch, and substitute in the value of the "remoteserver" property. It will also comment out the body of the "else" branch.

In the above example you were to run the following command:

XmlPreprocess /c /i web.config /d:remoteserver=productionserver1

The processor would write out


    <add key="server" value="productionserver1"/>

Another way to accomplish the same thing is to use an external settings file for each of your environments. The settings file is a simple XML document that contains a set of property/value pairs that should be substituted by the XML preprocessor. Here is what a settings file looks like:


  <property name="remoteserver">productionserver1<property>
  <property name="othersetting1">othersetting1<property>
  <property name="othersetting2">othersetting2<property>

To accomplish the same substitution as in the previous example using a settings file, the command line looks like this:

XmlPreprocess /c /i web.config /s settingsfile.xml

Global Properties

Properties can recursively resolve to other properties, this enables "global" variables in the settings file. For example:

  <property name="protocol">tcp</property>
  <property name="interchange_uri">${protocol}://server1</property>
  <property name="metadata_uri">${protocol}://server2</property>
  <property name="dataservice_uri">${protocol}://server3</property>

This property file would be fed into the preprocessor along with the original file which looks like this:

  <!-- #ifdef _xml_preprocess -->
  <!-- #endif -->

And the preprocessor would write out this:



Boolean Properties

By default, all property values are treated as strings with the exception of the word False (case is irrelevant). If you set a property to the value False, it will have the effect of un-defining it. There are some cases where you may actually want the literal value of "False" to be replaced. To accomplish this, enclose it in single or double quotes. The quotes will be stripped, and the value will simply be treated like any other string property.

This special handling of "False" can be changed by passing the /f or /fixfalse switch on the command line. This will treat "False" as a literal string. To undefine a property use a value of "#undef". This has been a long-standing request and has tripped up many users. To maintain drop-in backward compatibility of XmlPreprocess.exe, this change is off by default.

Built-In Properties

These properties are automatically defined by the processor and can be referred to within the configuration file without having to pass anything in. All built-in properties begin with an underscore.

Property Name Description
_xml_preprocess This property will always be defined whenever a file is being processed by the Xml Preprocessor
_dest_dir Directory portion of destination file. Example: d:\inetpub\wwwroot\web
_dest_root Expands to the root of the destination file path (ex: "C:\")
_machine_name Name of machine. Example: vmspap02caa
_machine_id Numeric portion of machine name. Example: 02
_os_platform Machine OS platform. Example: Win32NT
_os_version Machine OS version. Example: 5.1.2600.0
_system_dir Machine's system directory. Example: C:\WINNT\System32
_system_root Expands to the root of the system directory (ex: "C:\")
_current_dir Machine's current directory. Example: "C:\Installs
_current_root Expands to the root of the current directory as determined by Environment.CurrentDirectory (ex: "C:\")
_clr_version Gets the major, minor, build, and revision numbers of the common language runtime. Example: 1.1.4322
_user_name Gets the user name of the person who started the current thread. Example: EFudd
_user_domain_name Gets the network domain name associated with the current user. Example: MyDomain
_user_interactive Gets a value indicating whether the current process is running in user interactive mode. Example: True
_system_date System date. Example: 8/5/2003
_system_time System time. Example: 9:50 AM
_framework_dir .NET Framework directory. Example: C:\WINNT\Microsoft.NET\Framework\v1.1.4322
_environment_name Value passed in to the /e argument if there was one
_env_* Environment variables. Example: _ENV_PATH contains system's path environment variable.

Here is an example of these built-in properties:

  <!-- #ifdef _xml_preprocess -->
  <!-- <entry
    env_number_of_processors="${_env_number_of_processors}" />
  <!-- #endif -->

When processed this file would produce something similar to this:

    system_time="3:30 PM"
    env_number_of_processors="1" />

Dynamic Properties

Note: this is a new feature in version 2.0, Beta 4
You can use XPath and regular expression as dynamic properties. This enables you to perform replacements in your configuration "from the outside" in cases where you can not decorate the file with preprocessor comments, or when you want to make structural changes to your document like removing nodes or inserting XML.
Will set the compilation debug switch to False:

XmlPreprocess /i web.config /d ${Xpath=configuration/system.web/compilation/@debug}=False

Will replace all instances of the token @CaffeineDrink@ with Coffee

XmlPreprocess /i web.config /d ${RegEx=@CaffeineDrink@}=Coffee

This also works well from the spreadsheet, just use the dynamic property syntax in the property name column. See the binding sample for more examples.
More Example Property Names:

${Xpath=configuration/connectionStrings/add[@name ='LocalSqlServer']/@connectionString}=value
${Xpath=configuration/appSettings/add[@key ='SomeSwitch']/@value IncludedFiles=*.config}=value
${Xpath=configuration/appSettings IncludedFiles=*.foo}=value
${Xpath=configuration/appSettings/add[@key ='SomeSwitchToCompletelyRemove']}=#remove
${Xpath=//SomePlaceholder}=<SomeXML Foo="bar"/>

Last edited Aug 14, 2013 at 3:35 PM by lorenh, version 16


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