title: What does the error "the exec task needs a command to execute" mean?
body: <p>When compiling a project in Visual Studio, the error message "the exec task needs a command to execute"  appears, with no line number.  What does this error mean?</p>
  
  <p>(Apologies for asking and answering my own question; I just found an answer as I was writing this.  Have made it community wiki, so as not to offend.)</p>