Comparing two collections for equality irrespective of the order of items in them

Question

I would like to compare two collections (in C#), but I\'m not sure of the best way to implement this efficiently.

I\'ve read the other thread about Enumerable.Sequen

Answer 1

If comparing for the purpose of Unit Testing Assertions, it may make sense to throw some efficiency out the window and simply convert each list to a string representation (csv) before doing the comparison. That way, the default test Assertion message will display the differences within the error message.

Usage:

using Microsoft.VisualStudio.TestTools.UnitTesting;

// define collection1, collection2, ...

Assert.Equal(collection1.OrderBy(c=>c).ToCsv(), collection2.OrderBy(c=>c).ToCsv());

Helper Extension Method:

public static string ToCsv(
    this IEnumerable values,
    Func selector,
    string joinSeparator = ",")
{
    if (selector == null)
    {
        if (typeof(T) == typeof(Int16) ||
            typeof(T) == typeof(Int32) ||
            typeof(T) == typeof(Int64))
        {
            selector = (v) => Convert.ToInt64(v).ToStringInvariant();
        }
        else if (typeof(T) == typeof(decimal))
        {
            selector = (v) => Convert.ToDecimal(v).ToStringInvariant();
        }
        else if (typeof(T) == typeof(float) ||
                typeof(T) == typeof(double))
        {
            selector = (v) => Convert.ToDouble(v).ToString(CultureInfo.InvariantCulture);
        }
        else
        {
            selector = (v) => v.ToString();
        }
    }

    return String.Join(joinSeparator, values.Select(v => selector(v)));
}