1 files changed, 64 insertions, 0 deletions

diff --git a/src/WixToolset.Core/ProvidesDependencyCollection.cs b/src/WixToolset.Core/ProvidesDependencyCollection.cs
new file mode 100644
index 00000000..a777afb0
--- /dev/null
+++ b/src/WixToolset.Core/ProvidesDependencyCollection.cs
@@ -0,0 +1,64 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset
+{
+    using System;
+    using System.Collections.ObjectModel;
+
+    /// <summary>
+    /// A case-insensitive collection of unique <see cref="ProvidesDependency"/> objects.
+    /// </summary>
+    internal sealed class ProvidesDependencyCollection : KeyedCollection<string, ProvidesDependency>
+    {
+        /// <summary>
+        /// Creates a case-insensitive collection of unique <see cref="ProvidesDependency"/> objects.
+        /// </summary>
+        internal ProvidesDependencyCollection()
+            : base(StringComparer.InvariantCultureIgnoreCase)
+        {
+        }
+
+        /// <summary>
+        /// Adds the <see cref="ProvidesDependency"/> to the collection if it doesn't already exist.
+        /// </summary>
+        /// <param name="dependency">The <see cref="ProvidesDependency"/> to add to the collection.</param>
+        /// <returns>True if the <see cref="ProvidesDependency"/> was added to the collection; otherwise, false.</returns>
+        /// <exception cref="ArgumentNullException">The <paramref name="dependency"/> parameter is null.</exception>
+        internal bool Merge(ProvidesDependency dependency)
+        {
+            if (null == dependency)
+            {
+                throw new ArgumentNullException("dependency");
+            }
+
+            // If the dependency key is already in the collection, verify equality for a subset of properties.
+            if (this.Contains(dependency.Key))
+            {
+                ProvidesDependency current = this[dependency.Key];
+                if (!current.Equals(dependency))
+                {
+                    return false;
+                }
+            }
+
+            base.Add(dependency);
+            return true;
+        }
+
+        /// <summary>
+        /// Gets the <see cref="ProvidesDependency.Key"/> for the <paramref name="dependency"/>.
+        /// </summary>
+        /// <param name="dependency">The dependency to index.</param>
+        /// <exception cref="ArgumentNullException">The <paramref name="dependency"/> parameter is null.</exception>
+        /// <returns>The <see cref="ProvidesDependency.Key"/> for the <paramref name="dependency"/>.</returns>
+        protected override string GetKeyForItem(ProvidesDependency dependency)
+        {
+            if (null == dependency)
+            {
+                throw new ArgumentNullException("dependency");
+            }
+
+            return dependency.Key;
+        }
+    }
+}