MSBuild: Read and Write from a File to a Variable

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/msbuild_read_and_write_from_a_file_to_a_variable.htm]

MSBuild lets you easily read and write values from files into variables. While you could write your own custom tasks to do this, MSBuild provides out-of-the-box functionality with the ReadLinesFromFile and WriteLinesToFile tasks.

You can read from a file into a variable:

    <ReadLinesFromFile File="Version.txt">
      <Output TaskParameter="Lines"
        PropertyName="Prop1" />
    ReadLinesFromFile>

This will store the contents of the file "Version.txt" in a dynamically created property "Prop1".

You can also write to files:

      <WriteLinesToFile File="myFile.txt" Lines="This is a test value." Overwrite="false" />
      <WriteLinesToFile File="myFile.txt" Lines="A second line." Overwrite="false" />