Error while deleting keys from SPWebConfigModification

Question

I got following error when I tried to remove item from the WebConfigModification.

Exception calling "Remove" with "1" argument(s): "Object reference not set to a n instance of an object."

I need to remove all the entries from webConfigModification where owner is PowerShell.

$webApp = Get-SPWebApplication "myhomesite.com"
$webApp.WebConfigModifications

**This returns:**

Name                        : add[@key="RedirectToHelloPage"]
Path                        : configuration/appSettings
Sequence                    : 0
Owner                       : PowerShell
Value                       : <add key="RedirectToHelloPage" value="Hello.aspx" />
Type                        : EnsureChildNode
UpgradedPersistedProperties : {}

Name                        : add[@key="IsString"]
Path                        : configuration/appSettings
Sequence                    : 0
Owner                       : PowerShell
Value                       : <add key="IsString" value="false" />
Type                        : EnsureChildNode
UpgradedPersistedProperties : {}

Name                        : add[@key="IsString"]
Path                        : configuration/appSettings
Sequence                    : 0
Owner                       : PowerShell112
Value                       : <add key="IsString" value="false" >
Type                        : EnsureChildNode
UpgradedPersistedProperties : {}

And I want to Remove all entries with Owner = PowerShell

$config = $webApp.WebConfigModifications | Where-Object {$_.Owner -eq "PowerShell"}
$webApp.WebConfigModifications.Remove($config)
$webApp.Update()
$webApp.Parent.ApplyWebConfigModifications()

$config contains:

PS C:\> write-host $config
Microsoft.SharePoint.Administration.SPWebConfigModification

But I always get above mentioned error: Can somebody help?

Answer 1

There is an example on Technet illustrating how to remove WebConfigurationSection's in PowerShell here.

This will delete all entries, but you could easily change it to work for specific sections:

#=================================================================== 
# function to remove all existing node and changes to attributes matching the Owner name 
#=================================================================== 
function DeleteSections($webapp, $Owner, $removeOnly) 
{ 
    $count =  $webapp.WebConfigModifications.Count 
    $foundNodes = $false 
    for ($i=$count ;$i -gt -1; $i--) 
    { 
        if ($webapp.WebConfigModifications[$i].Owner -eq $Owner) 
        { 
            $foundNodes = $true 
            Write-Host "`n$i" 
            $webapp.WebConfigModifications.Remove($webapp.WebConfigModifications[$i]) 
        } 
    } 

    if ($foundNodes -and $removeOnly) 
    { 
        $webapp.Parent.ApplyWebConfigModifications() 
        $webapp.Update() 
    } 
} 

Answer 2

For others that find this thread due to searching for the "Object reference not set" error when trying to call SPWebConfigModifications.Remove... In my case this was caused by the SPWebConfigModification being created with a null value for the 'name' property. I had to programmatically set the name (make sure it is unique). Then I could remove the item.