Two small SPListItem extension methods

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Two small SPListItem extension methods

On July 15, 2010, in Articles Review, by ronald h

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So, it is about two small additional room methods which do basically the same job – getting a point field value from a SPListItem instance. Since LINQ to SharePoint is still not reasonably standard (let’s see if SharePoint 2010 will exchange that) the SPListItem indexer is the usual way to get the data from a SharePoint list item. It does the job but its main disadvantage is that it operates with objects which means no type safety, cumbersome code, type casts, additional checks, etc.

These two additional room methods are generics methods as well – so in the generics parameter you basically specify the return type of the method. And why two – it’s simple – because of the huge dichotomy in .NET types – reference and value types. The first method works with reference field value types, the second one with value types (check out the where clause in the methods’ declarations). And the latter’s return type is not really the generics parameter type but its Nullable counterpart – the SPListItem’s indexer is always probable to return null-s, isn’t it?

    1     public static class ListItemHelper
    2     {
    3         public static T GetValue<T>(this SPListItem item, string fieldName) where T : class
    4         {
    5             object o = item[fieldName];
    6             if (o == null || !(o is T)) return null;
    7             return (T)o;
    8         }
    9 
   10         public static Nullable<T> GetValue2<T>(this SPListItem item, string fieldName) where T : struct
   11         {
   12             object o = item[fieldName];
   13             if (o == null || !(o is T)) return null;
   14             return (Nullable<T>)(T)o;
   15         }
   16     }

And here’s a small sample of how to use the methods:

    1     SPListItem it = list.Items[0];
    2     string title = it.GetValue<string>("Title");
    3     DateTime? made = it.GetValue2<DateTime>("Made");