In a Cmdlet, how can I detect if the Debug flag is set?

Question

I\'m writing a PowerShell Cmdlet and using WriteDebug, but I want to write an object which requires an extra API call, and I\'d rather not make that call when debugging is t

Answer 1

Experimentation indicates you might want to look at the $DebugPreference variable. I tried it with advanced functions, but it probably works just as well in a cmdlet.

Try the following sequence of commands:

function f { [cmdletbinding()]Param() $DebugPreference }
function g { [cmdletbinding()]Param() f }
f
f -Debug
g
g -Debug

Answer 2

Just checking if the -Debug flag is set can be done with the code below, but it is not enough.

bool debug = false;
bool containsDebug = MyInvocation.BoundParameters.ContainsKey("Debug");
if (containsDebug)
    debug = ((SwitchParameter)MyInvocation.BoundParameters["Debug"]).ToBool();

PowerShell also allows you to set a global flag called $DebugPreference which the code above does not check. And calling a cmdlet from another cmdlet inherits these common parameters which is not inherited through the Debug flag as the code above checks. The code below will check $DebugPreference and solves those problems.

debug = (ActionPreference)GetVariableValue("DebugPreference") != ActionPreference.SilentlyContinue;

Unfortunately in contrary to a cmdlet in PowerShell you have to check both. So the final C# code is as below. I have also added the code for the Verbose common parameter as bonus. Be sure to inherit from PSCmdlet instead of Cmdlet to get to the GetVariableValue method.

bool debug = false;
bool containsDebug = MyInvocation.BoundParameters.ContainsKey("Debug");
if (containsDebug)
    debug = ((SwitchParameter)MyInvocation.BoundParameters["Debug"]).ToBool();
else
    debug = (ActionPreference)GetVariableValue("DebugPreference") != ActionPreference.SilentlyContinue;

bool verbose = false;
bool containsVerbose = MyInvocation.BoundParameters.ContainsKey("Verbose");
if (containsVerbose)
    verbose = ((SwitchParameter)MyInvocation.BoundParameters["Verbose"]).ToBool();
else
    verbose = (ActionPreference)GetVariableValue("VerbosePreference") != ActionPreference.SilentlyContinue; 

Answer 3

Try this:

$Debug = $psboundparameters.debug.ispresent


if ($Debug){
  Write-Debug(string.Format("Name : {0}", api.GetName(myobj))
  }

Answer 4

To access the Debug flag from C# you should be able to do essentially the same thing as mjolinor suggests:

if (this.MyInvocation.BoundParameters.ContainsKey("Debug"))
{
    ... do something ...
}

However, note that you can specify the debug parameter with a value of false:

MyCmdlet -Debug:$false

To handle this case, you probably want to add something like this (from within the PSCmdlet):

bool debug = MyInvocation.BoundParameters.ContainsKey("Debug") &&
             ((SwitchParameter)MyInvocation.BoundParameters["Debug"]).ToBool();

In C# BoundParameters is a dictionary, so you could also use TryGetValue(), but note that the value of a switch (like Debug) is a SwitchParameter not a bool.

for further information see the following:

• PSCmdlet.MyInvocation: http://msdn.microsoft.com/en-us/library/system.management.automation.pscmdlet.myinvocation(v=vs.85).aspx
• BoundParameters: http://msdn.microsoft.com/en-us/library/system.management.automation.invocationinfo.boundparameters(v=vs.85).aspx
• SwitchParameter: http://msdn.microsoft.com/en-us/library/windows/desktop/system.management.automation.switchparameter(v=vs.85).aspx