{"id":107974,"date":"2023-03-27T07:00:00","date_gmt":"2023-03-27T14:00:00","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/oldnewthing\/?p=107974"},"modified":"2023-03-26T19:50:17","modified_gmt":"2023-03-27T02:50:17","slug":"20230327-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20230327-00\/?p=107974","title":{"rendered":"Using the contents of a file to define an MSBuild property"},"content":{"rendered":"

Say you want to define a property in your MSBuild project file (vcxproj, csproj, etc.) and have the property value come from a file. You might try using the Read\u00adLines\u00adFrom\u00adFile<\/code> task to get the contents:<\/p>\n

  <Target Name=\"DefineMagic\">\r\n    <ReadLinesFromFile File=\".\\magic.txt\">\r\n      <Output TaskParameter=\"Lines\" PropertyName=\"Magic\" \/>\r\n    <\/ReadLinesFromFile>\r\n  <\/Target>\r\n  <ItemDefinitionGroup>\r\n    <ClCompile>\r\n      <PreprocessorDefinitions>MAGIC=\"$(Magic)\";%(PreprocessorDefinitions)<\/PreprocessorDefinitions>\r\n    <\/ClCompile>\r\n  <\/ItemDefinitionGroup>\r\n<\/pre>\n
This doesn’t work because the Target<\/code> doesn’t run until after the Item\u00adDefinition\u00adGroup<\/code> is already defined. MSBuild evaluates Property\u00adGroup<\/code> and Item\u00adGroup<\/code> elements before running any Target<\/code>s, By the time you execute the Read\u00adLines\u00adFrom\u00adFile<\/code> task, it’s too late.<\/p>\n
Instead, you can use the Read\u00adAll\u00adText<\/code>  MSBuild property function<\/a> to read the text into a property.<\/p>\n
  <PropertyGroup>\r\n    <Magic>$([System.IO.File]::ReadAllText('.\\magic.txt').TrimEnd())<\/Magic>\r\n  <\/PropertyGroup>\r\n  <ItemDefinitionGroup>\r\n    <ClCompile>\r\n      <PreprocessorDefinitions>MAGIC=\"$(Magic)\";%(PreprocessorDefinitions)<\/PreprocessorDefinitions>\r\n    <\/ClCompile>\r\n  <\/ItemDefinitionGroup>\r\n<\/pre>\n
You can see an example of this trick in the  WindowsAppSDK build properties<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
A little trick that maybe should be better known.<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-107974","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
A little trick that maybe should be better known.<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/107974","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=107974"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/107974\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=107974"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=107974"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=107974"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}