Why can't I define 2 site columns to have the same Display names but have different Internal names

Question

I am working on a sharepoint server 2016 on-premise. I have the following scenario, which I can not understand:-

1. Using the UI from "Site settings" >> "Site columns". I created a new site column named ITDepartmentOwner.
2. Now I got a new site column with the following properties:-
   • Display & Internal Name = ITDepartmentOwner.
3. now using the UI I rename the site column to be IT Department Owner by adding white spaces between the words.
4. now the column properties are as follow:-
   • Internal name did not change = ITDepartmentOwner
   • Display name = IT Department Owner .

now I do understand that modifying a column name will only affect its display name while the internal name will not get changed, and this is fine. but the problem I am facing is that, when I try to rename my site column to be Owner, I got the following error:-

So I am not sure why I got this error. Now SharePoint should allow having duplicate Display names, but not duplicate Internal names... and in my case I want to rename my site column to be Owner.. but since I have another column with this name I got the error.. but still the 2 columns have different internal names.. so I am not sure what I can do ? now one way I find to fix this temporary is to rename the column at the list level from IT Department Owner to Owner.. where I did not get any error message.. but still I want this renaming to be done at the site level... so can anyone adivce on the above problem please?

Answer 1

Because you have to use unique DisplayNames for Calculated Column Formulas
(and internal Computed Columns you don't see those in the UI)

So there is a check for Duplicate names in a lot of (UI) code

You can change DisplayNames with code.. CSOM, JSOM, REST, whatever you prefer:

My (private) CalcMaster tool does it (Column3 renamed to Column1) for Calculated Columns,
it works for all Custom Columns

But I strongly advice not to do it, because any Update through the UI will no longer work .. so you have to do everything with code

---

Proof it can be done:

[Column1] = "One"

[Column2] = [Column1] It uses the first Column1

[Column1] (Column3) ="Three"

Answer 2

Use below PowerShell script and try to search the name in "Title" (Display Name) field. If the name exists there, then you can't use that name.

Add-PsSnapin Microsoft.SharePoint.PowerShell 
## SharePoint DLL++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++Start 
[void][System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint")  

# Give Your Site Collection URL 

$url= "http://demoSite" 

# Code to Get the current working directory and generate the file Name with Current Date and Time + SiteColumnDetails.CSV 
function Get-ScriptDirectory 
{ 
    $Invocation = (Get-Variable MyInvocation -Scope 1).Value 
    Split-Path $Invocation.MyCommand.Path 
}  
$localFolderObject = Get-ScriptDirectory 
$localFolder = $localFolderObject.ToString() + "\" 
#Get current working directory 
$today = Get-Date 
$fileName = $localFolder + $today.Day.ToString() + "-" + $today.month.ToString() + "-" + $today.year.ToString() + "--SiteColumnDetails.csv" 


#Writing the CSV Column Header  - Tab Separated 
 "Column Title `t Site Column ID `t InternalName `t StaticName `t MaxLength `t Description `t Group `t TypeShortDescription " | out-file $fileName 


#Operation+++++++++++++++++++++++++++++++++++++++++++++++++++Start 
$site   =    new-object Microsoft.SharePoint.SPSite($url) 
$web    = $site.rootweb.Fields 
echo "Generating File..." 
ForEach ($id in $web) 
{ 

"$($id.Title) `t $($id.Id) `t $($id.InternalName) `t $($id.StaticName) `t $($id.MaxLength)/$($id.MaxLength) `t $($id.Description) `t $($id.Group) `t $($id.TypeShortDescription) " | Out-File $fileName -Append 

} 
$site.Dispose() 

#Operation+++++++++++++++++++++++++++++++++++++++++++++++++++Start 
echo "CSV file generated successfully, please check the below given path" 
echo "File created at : + $fileName "

Answer 3

Enter New name and run this in the browser console

function ValidateAndSubmit() {  
       return true; 
    }
    function doesFieldNameConflict(strName) {
        return false; 
    }

You will be now able to save the name.