Programmatically Hiding a Content Type Field

Question

Here is my scenario,
I have 2 content types (CT1 and CT2). CT2 is created programmatically using PowerShell by the lines of code given below,
$CT1= $spWeb.ContentTypes["My Content Type 1"]
$CT2 = $spWeb.ContentTypes["My Content Type 2"]
if($CT2 -eq $null)
$CT2 =New-Object Microsoft.SharePoint.SPContentType -ArgumentList @($CT1, $spWeb.ContentTypes, "My Content Type 2");
$CT2.Group = "My Group";
$CT2.Description = "Some Description for CT2.";
$spWeb.ContentTypes.Add($CT2);
I want to hide some of the columns that I inherited from CT1 in CT2. When I use the below code for hiding columns, I get 'Exception setting "Hidden": "Cannot
change Hidden attribute for this field"'
<pre lang="x-powershell">$field = $CT2.Fields["MyField"] #MyField - I want to hide this field
$field.Hidden = $true;
$field.Update()
After I looked deeper into the problem, I found that, CanToggleHidden property for the field is set to 'False'. Hence, I decided to change the flag using reflection by using the lines below,
$field = $CT2.Fields["MyField"] #MyField - I want to hide this field
$bindingFlags = [Reflection.BindingFlags] "NonPublic,Instance"
[System.Type] $type = $field.GetType();
[Reflection.MethodInfo] $mdInfo = $type.GetMethod("SetFieldBoolValue",$bindingFlags);
$object = [System.Object] @("CanToggleHidden",$true);
$mdInfo.Invoke($field,$object);
$field.Hidden = $true;
$field.Update()
This time, I did not get error at $field.Hidden but at $field.Update() method call, I get 'Exception calling "Update" with "0" argument(s): "This functionality
is unavailable for fields not associated with a list."'
Suprisingly from UI (Site Settings -> Site Content Types), I can browse to 'CT2' content type and hide columns that I don't want!!!!
My questions is, Is there a way to hide unwanted columns programmatically?
SSK

Answer 1

You should reference the field you want to hide not from the Fields collection, but from the FieldLinks one.
Try to change powershell string:
$field = $CT2.Fields["MyField"]
to this one:
$field = $CT2.FieldLinks["MyField"]
After it, the script should work without exceptions.