Implement MCP task support (SEP-1686) (#1170)

Co-authored-by: Stephen Halter <halter73@gmail.com>

src/ModelContextProtocol/McpServerServiceCollectionExtensions.cs

@@ -26,6 +26,17 @@ public static class McpServerServiceCollectionExtensions
             services.Configure(configureOptions);
         }
 
+        // Register IMcpTaskStore from options if not already registered.
+        // This allows users to either:
+        // 1. Register IMcpTaskStore directly in DI (takes precedence)
+        // 2. Set options.TaskStore in the configuration callback (used as fallback)
+        // If neither is done, resolving IMcpTaskStore will throw.
+        services.TryAddSingleton<IMcpTaskStore>(sp =>
+        {
+            var options = sp.GetRequiredService<IOptions<McpServerOptions>>().Value;
+            return options.TaskStore ?? throw new InvalidOperationException("No IMcpTaskStore has been configured. Either register an IMcpTaskStore in the service collection or set McpServerOptions.TaskStore when configuring the MCP server.");
+        });
+
         return new DefaultMcpServerBuilder(services);
     }
 }

src/ModelContextProtocol/ModelContextProtocol.csproj

@@ -7,6 +7,8 @@
     <PackageId>ModelContextProtocol</PackageId>
     <Description>.NET SDK for the Model Context Protocol (MCP) with hosting and dependency injection extensions.</Description>
     <PackageReadmeFile>README.md</PackageReadmeFile>
+    <!-- Suppress the experimental tasks warning -->
+    <NoWarn>$(NoWarn);MCPEXP001</NoWarn>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard2.0'">