/mcs/class/System.ComponentModel.Composition/Tests/UnitTestFramework/System/Collections/EnumerableExtensions.cs

// -----------------------------------------------------------------------

// Copyright (c) Microsoft Corporation.  All rights reserved.

// -----------------------------------------------------------------------

using System;

using System.Collections;

using System.Collections.Generic;

using Microsoft.VisualStudio.TestTools.UnitTesting;



namespace Microsoft.Internal.Collections

{

    public static class EnumerableExtensions

    {

        public static int Count(this IEnumerable source)

        {

            int count = 0;



            foreach (object o in source)

            {

                count++;

            }



            return count;

        }



        public static IEnumerable<T> ToEnumerable<T>(this IEnumerable source)

        {

            foreach (object value in source)

            {

                yield return (T)value;

            }

        }



        public static List<object> ToList(this IEnumerable source)

        {

            var enumerable = source.ToEnumerable<object>();



            return System.Linq.Enumerable.ToList(enumerable);

        }



        public static T AssertSingle<T>(this IEnumerable<T> source)

        {

            return AssertSingle(source, t => true);

        }



        public static T AssertSingle<T>(this IEnumerable<T> source, string message)

        {

            return AssertSingle(source, t => true, message);

        }



        public static T AssertSingle<T>(this IEnumerable<T> source, Func<T, bool> predicate)

        {

            return AssertSingle(source, predicate, "Expecting a single item matching the predicate in the collection.");

        }



        public static T AssertSingle<T>(this IEnumerable<T> source, Func<T, bool> predicate, string message)

        {

            int count = 0;

            T ret = default(T);

            foreach (T t in source)

            {

                if (predicate(t))

                {

                    count++;

                    ret = t;

                }

            }



            Assert.AreEqual(1, count, message);

            return ret;

        }

    }

}