Use relative paths for working directory & start in C# project

Edit directly in the .csproj file without escaping the characters, like this:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <ProjectView>ProjectFiles</ProjectView>
  </PropertyGroup>
  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'">
    <StartAction>Program</StartAction>
    <StartWorkingDirectory>$(SolutionDir)..\..\..\..\mydir</StartWorkingDirectory>
    <StartProgram>$(SolutionDir)..\..\dir\myapplication.exe</StartProgram>
  </PropertyGroup>
</Project>

Also there is no need for the slash after $(SolutionDir)

I know this might sound the same as others, I just want to be clear you did exactly this.

You should

1. close visual studio - it's important as it might override your file if you keep it open
2. open myproject.csproj.user using notepad.

3. enter this

   <?xml version="1.0" encoding="utf-8"?>
   <Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
     <PropertyGroup>
       <ProjectView>ProjectFiles</ProjectView>
     </PropertyGroup>
     <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'">
       <StartAction>Program</StartAction>
       <StartWorkingDirectory>$(SolutionDir)..\..\..\..\mydir</StartWorkingDirectory>
       <StartProgram>$(SolutionDir)..\..\dir\myapplication.exe</StartProgram>
     </PropertyGroup>
   </Project>
   

4. Close notepad

5. Open Visual Studio
6. Go to project properties and confim you see this