How to Prevent SharePoint List or Columns from Deletion?

Scenario: We've a configuration list being used by a custom SharePoint application and we don't want to let the users to delete the configuration list in SharePoint. So how to prevent delete in SharePoint list?

The idea is: Set the "AllowDeletion" property of the SharePoint list or Library to false. These properties can be set programmatically using object mode code C# or PowerShell.

PowerShell script to Disable Delete on SharePoint List or Library:

#Get the Web
$web = Get-SPWeb "http://sharepoint.crescent.com/sites/pmo"

#Get the List
$list = $web.Lists["Design Documents"]

#Set the "AllowDeletion" property
$List.AllowDeletion=$false
$List.Update()

"Delete this document library" or "Delete this list" link will go hidden under list settings!

We can use the C# code as well to disable delete option on SharePoint list and libraries:

using(SPSite site = new SPSite("http://sharepoint.crescent.com/sites/pmo"))
 {
  using(SPWeb web = site.OpenWeb())
   {
       SPList list = web.Lists["Design Documents];
       list.AllowDeletion = false;
       list.Update();
    }
 }

Same trick applies to SharePoint list columns as well. Sett the field's "AllowDeletion" property to false to prevent the field from deletion. Here is an example: Typical SharePoint list columns will look like:
Lets prevent the column from deletion by setting "AllowDeletion" property to false.

PowerShell script to disable delete on list columns:

#Get the Web
$web = Get-SPWeb "http://sharepoint.crescent.com/sites/pmo"

#Get the List
$list = $web.Lists["Design Documents"]

#Get the column
$column = $list.Fields["Category"]

#Disable Delete
$column.AllowDeletion = $false
$column.Update()
 
$web.Dispose()

Output:
Now, the reverse: Delete Button Missing in SharePoint Column? Here is How to Delete them.