Raghu's SharePoint Column : SharePoint - My Lifeline!!

Raghu's SharePoint Column

Create list with lookup column assosciated with the same list or other list.

I had run into a scenario where I need to have a lookup column in the same list and many views which are based on the look up column, at first I thought this is simple to implement, but once I started implementing it, I realized that it’s not so simple. I googled on net to find an alternate for my solution, but the soultions didn’t work for me.

Before entering the implementation part I would like to disccuss about lookup column archintecutre in list. Lookup column has two important attribute lookup list and the lookup field.

Lookup List: Indicates to which list the lookup filed should refer.
Lookup Field: Which column or filed need to be refferd or showed from the list specified above.

As a regular methodology I started implementing the list using feature since it would be easy to maintain views, I created a list using feature, b ut the prob was the lookup comun was not showing up any data. Later I came to know that internally look up column uses list id to keep the track of which list it should reffer. So I googled to find out how we can update the list id of a lookup column. You cannot update the lookup column using OOB UI if you have created a list using feature or list template. I went through the following blogs

1. http://www.sharepoint-tips.com/2007/04/fixing-lookup-fields-in-list-definition.html

2. https://www2.blogger.com/comment.g?blogID=20371103&postID=4251369915225974613

Since the lookup column requires List ID, there was no point in creating list using feature because the list id will be known only when the list is created.

I thought of another alternate is to create a list using feature and than to delete and create lookup column again by programmatically, but by doing this all my views related to the lookup column failed and when I tried to create a new item in the list, all the column which were created were not visible in the newform.aspx.

Finally I came up with a solution, which has a nice amount of coding effort. The solution was to create a list, lookup column and views programmatically (using code).

Here’s the code to fix the solution of Lookup Column in the same list.

SPList list = web.Lists[listName];
list.Fields.AddLookup("ParentMenu", list.ID, false);
SPFieldLookup parentMenu = (SPFieldLookup)list.Fields.GetField("ParentMenu");
parentMenu.LookupField = "MenuName";

Here’s the code to fix the solution of Lookup Column in other list.

SPList list = web.Lists[listName];
SPList newlist = web.Lists[newlistName];
list.Fields.AddLookup("ParentMenu", newlist.ID, false);
SPFieldLookup parentMenu = (SPFieldLookup)list.Fields.GetField("ParentMenu");
parentMenu.LookupField = "ColumnInNewList";

This is a work around and a long approach, feel free to respond or comment if u have any other alternate or better solution.


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