Fix regression matching templated McpServerResources (#897)

tests/ModelContextProtocol.Tests/Configuration/McpServerResourceRoutingTests.cs

@@ -0,0 +1,42 @@
+using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Client;
+using ModelContextProtocol.Protocol;
+using ModelContextProtocol.Server;
+
+namespace ModelContextProtocol.Tests.Configuration;
+
+public sealed class McpServerResourceRoutingTests(ITestOutputHelper testOutputHelper) : ClientServerTestBase(testOutputHelper)
+{
+    protected override void ConfigureServices(ServiceCollection services, IMcpServerBuilder mcpServerBuilder)
+    {
+        mcpServerBuilder.WithResources([
+            McpServerResource.Create(options: new() { UriTemplate = "test://resource/non-templated" } , method: () => "static"),
+            McpServerResource.Create(options: new() { UriTemplate = "test://resource/{id}" }, method: (string id) => $"template: {id}"),
+            McpServerResource.Create(options: new() { UriTemplate = "test://params{?a1,a2,a3}" }, method: (string a1, string a2, string a3) => $"params: {a1}, {a2}, {a3}"),
+        ]);
+    }
+
+    [Fact]
+    public async Task MultipleTemplatedResources_MatchesCorrectResource()
+    {
+        // Verify that when multiple templated resources exist, the correct one is matched based on the URI pattern, not just the first one.
+        // Regression test for https://github.com/modelcontextprotocol/csharp-sdk/issues/821.
+        await using McpClient client = await CreateMcpClientForServer();
+
+        var nonTemplatedResult = await client.ReadResourceAsync("test://resource/non-templated", TestContext.Current.CancellationToken);
+        Assert.Equal("static", ((TextResourceContents)nonTemplatedResult.Contents[0]).Text);
+
+        var templatedResult = await client.ReadResourceAsync("test://resource/12345", TestContext.Current.CancellationToken);
+        Assert.Equal("template: 12345", ((TextResourceContents)templatedResult.Contents[0]).Text);
+
+        var exactTemplatedResult = await client.ReadResourceAsync("test://resource/{id}", TestContext.Current.CancellationToken);
+        Assert.Equal("template: {id}", ((TextResourceContents)exactTemplatedResult.Contents[0]).Text);
+
+        var paramsResult = await client.ReadResourceAsync("test://params?a1=a&a2=b&a3=c", TestContext.Current.CancellationToken);
+        Assert.Equal("params: a, b, c", ((TextResourceContents)paramsResult.Contents[0]).Text);
+
+        var mcpEx = await Assert.ThrowsAsync<McpProtocolException>(async () => await client.ReadResourceAsync("test://params{?a1,a2,a3}", TestContext.Current.CancellationToken));
+        Assert.Equal(McpErrorCode.InvalidParams, mcpEx.ErrorCode);
+        Assert.Equal("Request failed (remote): Unknown resource URI: 'test://params{?a1,a2,a3}'", mcpEx.Message);
+    }
+}