<p>How can I get Environnment variables and if something is missing, set the value?</p>

Use the
System.Environment
class.
The methods
```
```
var value = System.Environment.GetEnvironmentVariable(variable [, Target])
```
```
and
```
```
System.Environment.SetEnvironmentVariable(variable, value [, Target])
```
```
will do the job for you.
The optional parameter
```
Target
```
is an enum of type
```
EnvironmentVariableTarget
```
and it can be one of:
```
Machine
```
,
```
Process
```
, or
```
User
```
. If you omit it, the default target is the
current process.