SharePoint uses a lot of field types that have different underlying schemas, delimiters and formats. I see a lot of people reverse engineer the field information and "hack" the data into the list using a string such as "1;#Title" for a lookup field. Well this isn't exactly best practice so I've put together a reference table below to assist in using the correct data types for populating or retrieving information from a SharePoint list.
Lookup Field
Field Class: SPFieldLookup
Field Value Class: SPFieldLookupValue
Populating Information:
item["FieldName"] = new SPFieldLookupValue("Title"); // SharePoint will do the lookup as long as the LookupValue's are unique
item.Update();
//or
item["FieldName"] = new SPFieldLookupValue(1, "Title");
item.Update();
Retrieving Information:
SPFieldLookupValue itemValue = item["FieldName"] as SPFieldLookupValue;
int id = itemValue.LookupId;
string value = itemValue.LookupValue;
Multiple Lookup Field
Field Class: SPFieldLookup
Field Value Class: SPFieldLookupValueCollection
Populating Information:
SPFieldLookupValueCollection itemValues = SPFieldLookupValueCollection();
itemValues.Add(new SPFieldLookupValue(1, "Title"));
item["FieldName"] = itemValues;
item.Update();
Retrieving Information:
SPFieldLookupValueCollection itemValues = item["FieldName"] as SPFieldLookupValueCollection;
foreach (SPFieldLookupValue itemValue in itemValues)
{
int id = itemValue.LookupId;
string value = itemValue.LookupValue;
}
User Field
Field Class: SPFieldUser
Field Value Class: SPFieldUserValue
Populating Information:
web.EnsureUser(@"domain\username");
SPUser user = web.AllUsers[@"domain\username"];
item["FieldName"] = user;
item.Update();
Retrieving Information:
string currentValue = item["FieldName"].ToString();
SPFieldUser userField = list.Fields.GetFieldByInternalName("FieldName");
SPFieldUserValue itemValue = (SPFieldUserValue)userField.GetFieldValue(currentValue);
SPUser user = itemValue.User;
URL Field
Field Class: SPFieldUrl
Field Value Class: SPFieldUrlValue
Populating Information:
SPFieldUrlValue urlValue = new SPFieldUrlValue();
urlValue.Url = "<a href="http://www.google.com/">http://www.google.com/</a>";
urlValue.Description = "Google";
item["FieldName"] = urlValue;
item.Update();
Retrieving Information:
SPFieldUrlValue urlValue = new SPFieldUrlValue(item["FieldName"].ToString());
string url = urlValue.Url;
string description = urlValue.Description;
Multiple Choice Field
Field Class: SPFieldMultiChoice
Field Value Class: SPFieldMultiChoiceValue
Populating Information:
SPFieldMultiChoiceValue itemValue = new SPFieldMultiChoiceValue();
itemValue.Add("Choice 1");
itemValue.Add("Choice 2");
itemValue.Add("Choice 3");
item["FieldName"] = itemValue;
item.Update();
Retrieving Information:
SPFieldMultiChoiceValue itemValue = new SPFieldMultiChoiceValue(item["FieldName"].ToString());
foreach (string choice in itemValue)
{
// value is in choice
}