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.
a. Open Visual Studio 2010.
b. Create Console application.
c. Replace the code with the following.