How to set system environment variable in C#?

Question

I\'m trying to set a system environment variable in my application, but get an SecurityException. I tested everything I found in google - without success. Here

Answer 1

In addition to David Heffernan's answer, here is a function that avoids a few gotchas for setting and appending a value to an environment variable:

void AddToEnvironmentVariable(string variable, string newValue, EnvironmentVariableTarget target)
{
    var content = Environment.GetEnvironmentVariable(variable, target) ?? string.Empty;
    if (content.Contains(newValue))
        return;

    var varBuilder = new StringBuilder(content);
    if (content != string.Empty && !content.EndsWith(';'))
        varBuilder.Append(";");
    varBuilder.Append(newValue);
    var finalValue = varBuilder.ToString();

    Environment.SetEnvironmentVariable(variable, finalValue, EnvironmentVariableTarget.Process);
    if (target != EnvironmentVariableTarget.Process)
        Environment.SetEnvironmentVariable(variable, finalValue, target);
}

It handles proper appending using ; and also ensures that subsequent calls to GetEnvironmentVariable contain the added value by setting in with the Processtarget.