How to enforce unique value for a column in SharePoint 2010 using powershell

In this article we will be seeing how to enforce unique value for a list or library column in SharePoint 2010 using C# and powershell.

In SharePoint 2010 we can enforce uniqueness on values in a list or library column, effectively creating a primary key. When you create a column in the list or library you could see an option "Enforce Unique Values" where you can enforce uniqueness. When you enforce uniqueness on a Lookup column, the list item in the target list can have only one list item looking up to it from the child list.

Using C#:

a. Open Visual Studio 2010.

b. Create Console application.

c. Replace the code with the following.

1. using System;

2. using System.Collections.Generic;

3. using System.Linq;

4. using System.Text;

5. using Microsoft.SharePoint;

6. namespace EnforceUniqueValue

7. {

8. class Program   

9. {

10. static void Main(string[] args)       

11. {

12. using (SPSite site = new SPSite("http://serverName:1111/"))           

13. {

14. using (SPWeb web = site.RootWeb)               

15. {

16. SPList list = web.Lists.TryGetList("cl");

17. SPField field = list.Fields["TestCol"];                   

18. field.Indexed = true;                   

19. field.EnforceUniqueValues = true;                   

20. field.Update();               

21. }           

22. }       

23. }   

24. }

25. }

d. Hit F5.

Using PowerShell:

1. $siteURL="http://serverName:1111/"

2. $listName="cl"

3. $fieldName="TestCol"

4. $site=Get-SPSite $siteURL

5. $web=$site.RootWeb

6. $list=$web.Lists.TryGetList($listName)

7. $field=$list.Fields[$fieldName]

8. $field.Indexed=$true

9. $field.EnforceUniqueValues=$true

10. $field.Update()