Add OfType method and tests

ShittyLINQ/OfType.cs

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+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace ShittyLINQ
+{
+    public static partial class Extensions
+    {
+        public static IEnumerable<TResult> OfType<TResult>(this IEnumerable self)
+        {
+            if (self == null) throw new ArgumentNullException();
+            return OfTypeIterator<TResult>(self);
+        }
+
+        private static IEnumerable<TResult> OfTypeIterator<TResult>(IEnumerable source)
+        {
+            foreach (object obj in source)
+            {
+                if (obj is TResult) yield return (TResult)obj;
+            }
+        }
+    }
+}

ShittyLINQ/ToArray.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+
+namespace ShittyLINQ
+{
+    public static partial class Extensions
+    {
+        public static TSource[] ToArray<TSource>(this IEnumerable<TSource> source)
+        {
+            if (source == null) throw new ArgumentNullException();
+            return new Buffer<TSource>(source).ToArray();
+        }
+    }
+
+    internal struct Buffer<TElement>
+    {
+        internal TElement[] items;
+        internal int count;
+
+        internal Buffer(IEnumerable<TElement> source)
+        {
+            TElement[] items = null;
+            int count = 0;
+            ICollection<TElement> collection = source as ICollection<TElement>;
+            if (collection != null)
+            {
+                count = collection.Count;
+                if (count > 0)
+                {
+                    items = new TElement[count];
+                    collection.CopyTo(items, 0);
+                }
+            }
+            else
+            {
+                foreach (TElement item in source)
+                {
+                    if (items == null)
+                    {
+                        items = new TElement[4];
+                    }
+                    else if (items.Length == count)
+                    {
+                        TElement[] newItems = new TElement[checked(count * 2)];
+                        Array.Copy(items, 0, newItems, 0, count);
+                        items = newItems;
+                    }
+                    items[count] = item;
+                    count++;
+                }
+            }
+            this.items = items;
+            this.count = count;
+        }
+
+        internal TElement[] ToArray()
+        {
+            if (count == 0) return new TElement[0];
+            if (items.Length == count) return items;
+            TElement[] result = new TElement[count];
+            Array.Copy(items, 0, result, 0, count);
+            return result;
+        }
+    }
+}

ShittyLinqTests/OfTypeTests.cs

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+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using ShittyLINQ;
+using System;
+using System.Collections.Generic;
+
+namespace ShittyTests
+{
+    [TestClass]
+    public class OfTypeTests
+    {
+        [TestMethod]
+        public void OfType_OfTypeFound()
+        {
+            object[] numbers = new object[] { 1, 2, 3, 4, 5 };
+            int expectedResult = 5;
+
+            IEnumerable<int> result = numbers.OfType<int>();
+
+            Assert.AreEqual(expectedResult, result.Count());
+        }
+
+        [TestMethod]
+        public void OfType_OfTypeNotFound()
+        {
+            object[] numbers = new object[] { 1, 2, 3, 4, 5 };
+            int expectedResult = 0;
+
+            IEnumerable<string> result = numbers.OfType<string>();
+
+            Assert.AreEqual(expectedResult, result.Count());
+        }
+
+        [TestMethod]
+        public void OfType_OfTypeSomeFound()
+        {
+            object[] numbers = new object[] { 1, 2, "3", 4, 5 };
+            int expectedResult = 1;
+
+            IEnumerable<string> result = numbers.OfType<string>();
+
+            Assert.AreEqual(expectedResult, result.Count());
+        }
+
+        [TestMethod]
+        [ExpectedException(typeof(ArgumentNullException))]
+        public void OfType_SourceIsNull()
+        {
+            int[] numbers = null;
+
+            IEnumerable<int> result = numbers.OfType<int>();
+        }
+    }
+}

ShittyLinqTests/ToArrayTests.cs

@@ -0,0 +1,35 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using ShittyLINQ;
+using ShittyTests.TestHelpers;
+using System;
+using System.Collections.Generic;
+
+namespace ShittyTests
+{
+    [TestClass]
+    public class ToArrayTests
+    {
+        [TestMethod]
+        public void ToArray_SequenceIsNull()
+        {
+            IEnumerable<int> nums = null;
+            Assert.ThrowsException<ArgumentNullException>(() => nums.ToArray());
+        }
+
+        [TestMethod]
+        public void ToArray_SequenceEquals()
+        {
+            IEnumerable<int> expected = new List<int> { 0, 1, 2 };
+            int[] actual = expected.ToArray();
+            TestHelper.AssertCollectionsAreSame(expected, actual);
+        }
+
+        [TestMethod]
+        public void ToArray_SequenceIsEmpty()
+        {
+            IEnumerable<int> expected = new List<int>();
+            int[] actual = expected.ToArray();
+            TestHelper.AssertCollectionsAreSame(expected, actual);
+        }
+    }
+}