Check if all List Items have the same member value in C#

Question

I\'m searching for a simple and fast way to check if all my Listitems have the same value for a member.

foreach (Item item in MyList)
{
    Item.MyMember = &         


        

Answer 1

Here is a generic one that works for all version of .NET beginning with 2.0:

public static bool AllSameByProperty(IEnumerable items, Converter converter)
{
    TProperty value = default(TProperty);
    bool first = true;

    foreach (TItem item in items)
    {
        if (first)
        {
            value = converter.Invoke(item);
            first = false;
            continue;
        }

        TProperty newValue = converter.Invoke(item); 

        if(value == null)
        {
            if(newValue != null)
            {
                return false;
            } 

            continue;
        }

        if (!value.Equals(newValue))
        {
            return false;
        }
    }

    return true;
}

Its usage in C# 2.0:

AllSameByProperty(list, delegate(MyType t) { return t.MyProperty; });

Its usage in C# 3.0:

AllSameByProperty(list, t => t.MyProperty);