Fix uri primitive lookup

Author: eiriktsarpalis

src/ModelContextProtocol.Core/Server/McpServerPrimitiveCollection.cs

@@ -10,13 +10,16 @@ public class McpServerPrimitiveCollection<T> : ICollection<T>, IReadOnlyCollecti
     where T : IMcpServerPrimitive
 {
     /// <summary>Concurrent dictionary of primitives, indexed by their names.</summary>
-    private readonly ConcurrentDictionary<string, T> _primitives = [];
+    private readonly ConcurrentDictionary<string, T> _primitives;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="McpServerPrimitiveCollection{T}"/> class.
     /// </summary>
     public McpServerPrimitiveCollection()
     {
+        _primitives = typeof(T) == typeof(McpServerResource)
+            ? new(UriTemplate.UriTemplateComparer.Instance)
+            : new();
     }
 
     /// <summary>Occurs when the collection is changed.</summary>

src/ModelContextProtocol.Core/UriTemplate.cs

@@ -2,6 +2,7 @@
 using System.Buffers;
 #endif
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Runtime.CompilerServices;
 using System.Text;
@@ -453,4 +454,52 @@ static void AppendHex(ref DefaultInterpolatedStringHandler builder, char c)
             }
         }
     }
+
+    /// <summary>
+    /// Defines an equality comparer for Uri templates as follows:
+    /// 1. Non-templated Uris use regular System.Uri equality comparison (host name is case insensitive).
+    /// 2. Templated Uris use regular string equality.
+    /// 
+    /// We do this because non-templated resources are looked up directly from the resource dictionary
+    /// and we need to make sure equality is implemented correctly. Templated Uris are resolved using
+    /// linear traversal so there's no need for equality comparison to be fully accurate.
+    /// </summary>
+    public sealed class UriTemplateComparer : IEqualityComparer<string>
+    {
+        public static IEqualityComparer<string> Instance { get; } = new UriTemplateComparer();
+
+        public bool Equals(string? uriTemplate1, string? uriTemplate2)
+        {
+            if (TryParseAsNonTemplatedUri(uriTemplate1, out Uri? uri1) &&
+                TryParseAsNonTemplatedUri(uriTemplate2, out Uri? uri2))
+            {
+                return uri1 == uri2;
+            }
+
+            return string.Equals(uriTemplate1, uriTemplate2, StringComparison.Ordinal);
+        }
+
+        public int GetHashCode([DisallowNull] string uriTemplate)
+        {
+            if (TryParseAsNonTemplatedUri(uriTemplate, out Uri? uri))
+            {
+                return uri.GetHashCode();
+            }
+            else
+            {
+                return StringComparer.Ordinal.GetHashCode(uriTemplate);
+            }
+        }
+
+        private static bool TryParseAsNonTemplatedUri(string? uriTemplate, [NotNullWhen(true)] out Uri? uri)
+        {
+            if (uriTemplate is null || uriTemplate.Contains('{'))
+            {
+                uri = null;
+                return false;
+            }
+
+            return Uri.TryCreate(uriTemplate, UriKind.RelativeOrAbsolute, out uri);
+        }
+    }
 }

tests/ModelContextProtocol.Tests/Server/McpServerResourceTests.cs

@@ -280,6 +280,16 @@ public async Task UriTemplate_IsHostCaseInsensitive(string actualUri, string que
             TestContext.Current.CancellationToken));
     }
 
+    [Fact]
+    public async Task ResourceCollection_UsesCaseInsensitiveHostLookup()
+    {
+        McpServerResource t1 = McpServerResource.Create(() => "resource", new() { UriTemplate = "resource://MyCoolResource" });
+        McpServerResource t2 = McpServerResource.Create(() => "resource", new() { UriTemplate = "resource://MyCoolResource2" });
+        McpServerPrimitiveCollection<McpServerResource> collection = new() { t1, t2 };
+        Assert.True(collection.TryGetPrimitive("resource://mycoolresource", out McpServerResource? result));
+        Assert.Same(t1, result);
+    }
+
     [Fact]
     public void MimeType_DefaultsToOctetStream()
     {