As a matter of fact you can do this, but it is not as easy as you might think. You can create your own config transformation. I have just written a very detailed blog post at http://sedodream.com/2010/09/09/ExtendingXMLWebconfigConfigTransformation.aspx regarding this. But here are the hightlights:
- Create Class Library project
- Reference Web.Publishing.Tasks.dll (under %Program Files (x86)%MSBuild\Microsoft\VisualStudio\v10.0\Web folder)
- Extend Microsoft.Web.Publishing.Tasks.Transform class
- Implement the Apply() method
- Place the assembly in a well known location
- Use xdt:Import to make the new transform available
- Use transform
Here is the class I created to do this replace
namespace CustomTransformType
{
using System;
using System.Text.RegularExpressions;
using System.Xml;
using Microsoft.Web.Publishing.Tasks;
public class AttributeRegexReplace : Transform
{
private string pattern;
private string replacement;
private string attributeName;
protected string AttributeName
{
get
{
if (this.attributeName == null)
{
this.attributeName = this.GetArgumentValue("Attribute");
}
return this.attributeName;
}
}
protected string Pattern
{
get
{
if (this.pattern == null)
{
this.pattern = this.GetArgumentValue("Pattern");
}
return pattern;
}
}
protected string Replacement
{
get
{
if (this.replacement == null)
{
this.replacement = this.GetArgumentValue("Replacement");
}
return replacement;
}
}
protected string GetArgumentValue(string name)
{
// this extracts a value from the arguments provided
if (string.IsNullOrWhiteSpace(name))
{ throw new ArgumentNullException("name"); }
string result = null;
if (this.Arguments != null && this.Arguments.Count > 0)
{
foreach (string arg in this.Arguments)
{
if (!string.IsNullOrWhiteSpace(arg))
{
string trimmedArg = arg.Trim();
if (trimmedArg.ToUpperInvariant().StartsWith(name.ToUpperInvariant()))
{
int start = arg.IndexOf('\'');
int last = arg.LastIndexOf('\'');
if (start <= 0 || last <= 0 || last <= 0)
{
throw new ArgumentException("Expected two ['] characters");
}
string value = trimmedArg.Substring(start, last - start);
if (value != null)
{
// remove any leading or trailing '
value = value.Trim().TrimStart('\'').TrimStart('\'');
}
result = value;
}
}
}
}
return result;
}
protected override void Apply()
{
foreach (XmlAttribute att in this.TargetNode.Attributes)
{
if (string.Compare(att.Name, this.AttributeName, StringComparison.InvariantCultureIgnoreCase) == 0)
{
// get current value, perform the Regex
att.Value = Regex.Replace(att.Value, this.Pattern, this.Replacement);
}
}
}
}
}
Here is web.config
<?xml version="1.0"?>
<configuration>
<appSettings>
<add key="one" value="one"/>
<add key="two" value="partial-replace-here-end"/>
<add key="three" value="three here"/>
</appSettings>
</configuration>
Here is my config transform file
<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
<xdt:Import path="C:\Program Files (x86)\MSBuild\Custom\CustomTransformType.dll"
namespace="CustomTransformType" />
<appSettings>
<add key="one" value="one-replaced"
xdt:Transform="Replace"
xdt:Locator="Match(key)" />
<add key="two" value="two-replaced"
xdt:Transform="AttributeRegexReplace(Attribute='value', Pattern='here',Replacement='REPLACED')"
xdt:Locator="Match(key)"/>
</appSettings>
</configuration>
Here is the result after transformation
<?xml version="1.0"?>
<configuration>
<appSettings>
<add key="one" value="one-replaced"/>
<add key="two" value="partial-replace-REPLACED-end"/>
<add key="three" value="three here"/>
</appSettings>
</configuration>