MSBuild property and variable overloading

Question

Let's say I launch a build script, definition named SampleScript , specifying the parameter /p:MyPrefix=Custom. There is the following code in the script:

<PropertyGroup Condition="$(BuildDefinitionName)=='SampleScript'">
    <MyPrefix>Default</MyPrefix>
</PropertyGroup>

As I get, first MyPrefix is set to "Custom", then it's overloaded to "Default" (am I right?). If so, is there any way to make a user-specified parameter more prioritized, so it's not overloaded?

Answer 1

You can only overload a property specified on the command line by dynamically changing the value inside a target...

<Project ...>
   <PropertyGroup>
      <Value>FromStaticProperty</Value>
   </PropertyGroup>

   <Target Name="PropertyPrecedence">
      <Message Text="Value = '$(Value)'" />
      <PropertyGroup>
         <Value>FromDynamicProperty</Value>
      </PropertyGroup>
      <Message Text="Value = '$(Value)'" />
   </Target>
</Project>

> msbuild /p:Value=FromCommandLine

In the above example, the "FromStaticProperty" will be ignored given the value supplied from the command line, but the "FromDynamicProperty" will be used.

Excerpted from MSBuild Trickery trick #27