Question

An extension method on a collection named MeasurementCollection checks if the property Template.Frequency (Enum) of each item has the same value.

public static bool IsQuantized(this MeasurementCollection items)
{
    return  (from i in items 
             select i.Template.Frequency)
            .Distinct()
            .Count() == 1;
}

edit
info about underlying classes

MeasurementCollection : ICollection<IMeasurement>

IMeasurement 
{
    IMeasurementTemplate Template { get; }        
    ......
}

Is this a correct approach or is there an easier solution already in Linq?
This method will be used intense in the application.

Have you got tips to take with me, back to the drawing board?

Answer 1

Edit: to address Timwi’s concerns about 3 enumerators:

bool same = <your default> ;
var first = items.FirstOrDefault();
if (first != null)  // assuming it's a class
{
   same = items.Skip(1).All(i => i.Template.Frequency == first.Template.Frequency); 
}

Which still uses 2 enumerators. Not an issue for the average List<>, but for a DB query it might pay to use the less readable:

bool same = <your default> ;
Item first = null;

foreach(var item in items)
{
    if (first == null)
    {
        first = item;
        same = true;
    }
    else
    {
        if (item.Template.Frequency != first.Template.Frequency)
        {
           same = false;
           break;
        }
    }
}