Add the file to your project. In the properties, set build action to "content" and "copy to output directory" to "always".
Then under the Publish tab in the project properties, click on Application Files, and find the file. Change it from Include(Data) to Include(Required).
By default, ClickOnce sets XML files to be data, and puts them in an entirely different location than the assemblies.
If you include this in the top level of your project, you can find it by looking for
Path.Combine(System.Windows.Forms.Application.StartupPath, "myfilename.xml");
If you put it in a folder under your project, just append the folder to the startup path.
RobinDotNet
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