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Archive for June, 2011

Was making good progress with provisioning a site (with lists, content types, lookups, etc) in Sharepoint 2010, and thought I had the structural stuff licked. Moved on to the forms (dispform etc) and quickly found that I needed to include Dependant Lookups along with my Lookup Fields. This proved to be a bit tricky for me.

Dependant Lookups are new in Sharepoint 2010 and allow you to return virtual columns along with your Lookup Columns. They reveal themselves in the UI as checkboxes in the settings for Lookup Fields, and create additional columns in the format TargetList:SubColumn. So lets say I’ve got 2 lists: Customers and Orders that represent a one:many relationship. In Orders, I’ll need a Lookup Field (likely called “Customer”) that is a lookup to the Customers list.

On top of this, to make a parent-child form display correctly in the dispForm for Customers (ie a dispForm for a customer that shows all of their orders), I need to also reveal the ID of the Customer¬†in the lookup field in Orders. So when I look at my content type for the Orders list, there will be an entry “Customer” of type lookup, as well as as entry “Customer:ID” of type lookup.

So I wrote the following method to create the lookup, add any additional dependant lookups desired, and then return the lookup field to the calling method (so it can then add it to the content type, etc).

        /// <summary>
        /// Create a site column, at the specified web level, of type lookup and wire it up to the appropriate list and column.
        /// This creates the field, which will then be ready to be added to a content type and applied to a list.
        /// Note this must be done AFTER referenced list instances have been initiated.
        /// </summary>
        public static SPFieldLookup CreateLookupField(string fieldDisplayName, string fieldStaticName, string group, bool required, bool allowMultipleValues,
            string siteName, string webName, string lookupListName, string lookupField, List<string> DependentLookupFieldNames)
        {
            using (SPSite spSite = new SPSite(siteName))
            {
                using (SPWeb spWeb = spSite.OpenWeb(webName))
                {
                    SPList lookupList = spWeb.Lists[lookupListName];

                    spWeb.Fields.AddLookup(fieldStaticName, lookupList.ID, lookupList.ParentWeb.ID, required);
                    SPFieldLookup lookup = spWeb.Fields[fieldStaticName] as SPFieldLookup;
                    lookup.Title = fieldDisplayName; // "Title" is Display Name
                    lookup.AllowMultipleValues = allowMultipleValues;
                    lookup.LookupField = lookupField;
                    lookup.Group = group;
                    lookup.Indexed = true;
                    //lookup.RelationshipDeleteBehavior = SPRelationshipDeleteBehavior.Restrict;//"A site column cannot enforce a relationship behaviour"
                    lookup.StaticName = fieldStaticName;
                    lookup.Update(true);

                    if (DependentLookupFieldNames != null)
                    {
                        // Create the secondary columns. ie what's editable via the web ui reading:
                        // "Add a column to show each of these additional fields:" Displays like "Committee:ID"
                        // ie depField will usually be "ID"
                        foreach (string depField in DependentLookupFieldNames)
                        {
                            string dependantFieldName = spWeb.Fields.AddDependentLookup(string.Format("{0}:{1}", fieldDisplayName, depField), lookup.Id);// eg "Committee:ID"
                            SPFieldLookup dependentField = spWeb.Fields.GetFieldByInternalName(dependantFieldName) as SPFieldLookup;
                            dependentField.LookupField = depField;
                            dependentField.Group = group;
                            dependentField.Update(true);
                        }

                        spWeb.Update();
                    }

                    return lookup;
                }
            }
        }

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