IfNotNull.cs

// This is an attempt to implement the Null-propagating operator ?. as extension methods.
//
// I was not able to do it in a single method that would work with both value types and
// reference types as return type. Maybe there's a way to do it or use overloads?


public static class ExtensionMethods
{
   /// <summary>
   /// Use this method to safely invoke properties, methods or other members of a nullable
   /// object. It will perform a null reference check on the object and if it is not null will
   /// invoke the specified expression. The expression has to return a reference type.
   /// </summary>
   /// <returns>Returns a reference type.</returns>
   public static TResult IfNotNull<T, TResult>(this T obj, Func<T, TResult> func, Func<TResult> ifNull = null)
       where TResult : class
   {
       return (obj != null) ? func(obj) : (ifNull != null ? ifNull() : default(TResult));
   }

   /// <summary>
   /// Use this method to safely invoke properties, methods or other members of a nullable
   /// object. It will perform a null reference check on the object and if it is not null will
   /// invoke the specified expression. The expression has to return a value type.
   /// </summary>
   /// <returns>Returns a nullable value type.</returns>
   public static TResult? IfNotNullVal<T, TResult>(this T obj, Func<T, TResult> func, Func<TResult> ifNull = null)
       where TResult : struct
   {
       return (obj != null) ? func(obj) : (ifNull != null ? ifNull() : default(TResult));
   }
   
   public static void Dump(this object obj) {
   		Console.WriteLine(obj);
   }
}

void Main()
{
    // methods can be chained
    DateTime? dt = DateTime.Today;
    dt.IfNotNull(d => d.Value.ToLongDateString())
      .IfNotNull(s => s.ToUpper())
      .IfNotNull(s => s.PadLeft(40))
      .Dump();
	  
    // use this other method if a value type is retuned
    "STRING".IfNotNullVal(s => s.Length)
      .Dump();
}