How to run a target only it hasn't run?

I have a NAnt script like below:

&l开发者_运维技巧t;target name="Init" unless="${target::has-executed('Init')}">

What I want is to convert it into MSBuild script. What I can't do is to write MSBuild script to run a target only when it hasn't run like the above script.

Please help.

Targets only run once in an MSBUild build process. So just have a CallTarget element, and if it's already run, it will be skipped.