• There are two attributes from the xdt namespace that are used in the transformation:
  • The Locator attribute specifies how the element to be changed will be found.
    • If you do not specify a Locator attribute, the element to be changed is specified implicitly by the element that the Transform attribute is specified for.
    • There are three locator types:
      • Condition: an XPath expression that is evaluated relative to the current element.
      • Match: given a comma separated list of attribute names, will apply the transformation on elements whose attribute values match all of them.
      • XPath: Specifies an absolute XPath expression that is applied to the development Web.config file.
        • Unlike Condition, the expression that you specify is not appended to the implicit XPath expression that corresponds to the current element.
  • The Transform element specifies what is done with the element once we have it.

<connectionStrings>
	<add name="ConnectionName1" connectionString="newstring" providerName="newprovider"
	   xdt:Locator="Condition(@name='oldname' or @providerName='oldprovider')" xdt:Transform="Replace" />
	<add name="ConnectionName2" connectionString="newstring" providerName="newprovider"
       xdt:Locator="Match(name)" xdt:Transform="Replace" />
	<add name="ConnectionName3" connectionString="newstring" providerName="newprovider"
       xdt:Locator="XPath(configuration/connectionStrings[@name='ConnectionName3' 
		or @providerName='System.Data.SqlClient'])" xdt:Transform="Replace" />
</connectionStrings>

Transform Types

• Replace: Replaces the selected element with the element that is specified in the transform file.
  • If more than one element is selected, only the first selected element is replaced.
• Insert: Adds the element that is defined in the transform file as a sibling to the selected element or elements.
  • The new element is added at the end of any collection.
  • InsertIfMissing
  • InsertBefore
  • InsertAfter
• Remove: Removes the selected element. If multiple elements are selected, removes the first element.
  • RemoveAll
• RemoveAttributes: Removes specified attributes from the selected elements.
• SetAttributes: Sets attributes for selected elements to the specified values.
  • The SetAttributes attribute enables you to leave the element as it is but change selected attributes.
  • If you do not specify which attributes to change, all of the attributes that are present in the element in the transform file are changed.
  • The SetAttributes transform affects all selected elements.