Add users e-mail addresses from multivalue user field to string

Question

I have a list which contains a field users (Multivalues are allowed so it can contain multiple users)

I would like to retrieve the email addresses of all users and assign them to a string? Anyone some help on how to achive this with code behind (c#) in SharePoint 2010?

Answer 1

Assuming your field is a user/group field with multiple selections, the below code should get you started. I adapted the code found at http://gemsolution.blogspot.com/2009/04/fun-with-spfielduservaluecollection.html to your specs.

 StringBuilder allEmails = new StringBuilder();
 using (SPSite site = new SPSite("http://mysite.com/sitecollection"))
 {
     using (SPWeb web = site.OpenWeb("mysitename"))
     {
         SPList oList = web.Lists["ListName"];
         SPListItemCollection oListItems = oList.Items;
         foreach (SPListItem oListItem in oListItems)
         {
             //Gets a collection of all the User and Group objects from the UserGroup Field
             SPFieldUserValueCollection oFieldUserValueCollection =
                 new SPFieldUserValueCollection(web, oListItem["FieldName"].ToString());

             //Next, loop through the Values in the Collection
             foreach (SPFieldUserValue oFieldUserValue in oFieldUserValueCollection)
             {
                 //now we need to test if the SPFieldUserValue is a
                 //User or a  Group, because if we simply assign a user
                 //we will get a Null Reference Exception if it is a Group

                 //It is a Group
                 if (oFieldUserValue.User == null)
                 {
                     //Create and assign a new SPGroup object by using the
                     //Lookup value to return a Group from the current Site(SPWeb)
                     SPGroup oGroup = web.Groups.GetByID(oFieldUserValue.LookupId);
                 }
                 //It is a User
                 else
                 {
                     //Create and assign a new SPUSer object by using the User
                     //property of the SPFieldUserValue object
                     SPUser oUser = oFieldUserValue.User;
                     allEmails.Append(oUser.Email + ",");
                 }
             }
         }
     }

 }
 string allEmailsInAString = allEmails.ToString();