How can an application access the environment variable set by another application?

Question

In this case the application which sets the environment variable is executed in/from the application that needs to access the env.var. The Main() Return Values (C# Programming Guide) msdn article discusses its use within a batch file. If I try the same, everything is fine; but what is required is to run not from a batch script but from within an application.

Process.Start("app","args"); // app sets the env.var.
string envVar = System.Environment.GetEnvironmentVariable("ERRORLEVEL");

was obviously unsuccessful. Process.Start made the "app" work in a completely different environment I believe. In other words, I need to run "app" in the same environment as the caller application in order to reach the environment variable it sets.

Answer 1

If you're just trying to set the child's environment from the parent:

var p = new Process();
p.StartInfo.EnvironmentVariables["TEST_ENV"] = "From parent";
p.StartInfo.UseShellExecute = false;
p.StartInfo.FileName = @"C:\src\bin\Debug\ChildProc.exe";
p.Start();

If you don't want the child to inherit the parent process environment:

var psi = new ProcessStartInfo();
psi.EnvironmentVariables["TEST_ENV"] = "From parent";
psi.UseShellExecute = false;
psi.FileName = @"C:\src\bin\Debug\ChildProc.exe";
Process.Start(psi);