diff --git a/JsonRpc.Standard/Contracts/JsonRpcMethod.cs b/JsonRpc.Standard/Contracts/JsonRpcMethod.cs
index fbed72f..605a87d 100644
--- a/JsonRpc.Standard/Contracts/JsonRpcMethod.cs
+++ b/JsonRpc.Standard/Contracts/JsonRpcMethod.cs
@@ -92,7 +92,9 @@ internal object[] UnmarshalArguments(MarshaledRequest request)
                     continue;
                 }
                 // Resolve other parameters, considering the optional
-                var jarg = request.Message.Parameters?[this.Parameters[i].ParameterName];
+                var jarg = request.Message.Parameters.Type == JTokenType.Object
+                    ? request.Message.Parameters?[this.Parameters[i].ParameterName]
+                    : request.Message.Parameters?[i];
                 if (jarg == null)
                 {
                     if (this.Parameters[i].IsOptional)
diff --git a/JsonRpc.Standard/Contracts/RpcMethodBinder.cs b/JsonRpc.Standard/Contracts/RpcMethodBinder.cs
index 1956b18..7489440 100644
--- a/JsonRpc.Standard/Contracts/RpcMethodBinder.cs
+++ b/JsonRpc.Standard/Contracts/RpcMethodBinder.cs
@@ -1,4 +1,6 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using JsonRpc.Standard.Server;
@@ -31,15 +33,42 @@ internal class JsonRpcMethodBinder : IJsonRpcMethodBinder
         /// <inheritdoc />
         public JsonRpcMethod TryBindToMethod(ICollection<JsonRpcMethod> candidates, RequestContext context)
         {
-            //TODO Support array as params
             // context.Request.Parameters can be: {}, [], null (JValue), null
-            var paramsObj = context.Request.Parameters as JObject;
-            if (context.Request.Parameters is JArray) return null;
+            // Parameters MAY be omitted.
+            if (context.Request.Parameters == null || context.Request.Parameters.Type == JTokenType.Null)
+                return TryBindToParameterlessMethod(candidates);
+            // by-name
+            if (context.Request.Parameters is JObject paramsObj)
+                return TryBindToMethod(candidates, paramsObj);
+            // by-position
+            if (context.Request.Parameters is JArray paramsArray)
+                return TryBindToMethod(candidates, paramsArray);
+            // Other invalid cases, e.g., naked JValue.
+            return null;
+        }
+
+        private JsonRpcMethod TryBindToParameterlessMethod(ICollection<JsonRpcMethod> candidates)
+        {
+            JsonRpcMethod firstMatch = null;
+            foreach (var m in candidates)
+            {
+                if (m.Parameters.Count == 0 || m.Parameters.All(p => p.IsOptional))
+                {
+                    if (firstMatch != null) throw new AmbiguousMatchException();
+                    firstMatch = m;
+                }
+            }
+            return firstMatch;
+        }
+
+        private JsonRpcMethod TryBindToMethod(ICollection<JsonRpcMethod> candidates, JObject paramsObj)
+        {
+            Debug.Assert(paramsObj != null);
             JsonRpcMethod firstMatch = null;
             Dictionary<string, JToken> requestProp = null;
             foreach (var m in candidates)
             {
-                if (!m.AllowExtensionData && paramsObj != null)
+                if (!m.AllowExtensionData)
                 {
                     // Strict match
                     requestProp = paramsObj.Properties().ToDictionary(p => p.Name, p => p.Value);
@@ -64,5 +93,31 @@ public JsonRpcMethod TryBindToMethod(ICollection<JsonRpcMethod> candidates, Requ
             }
             return firstMatch;
         }
+
+        private JsonRpcMethod TryBindToMethod(ICollection<JsonRpcMethod> candidates, JArray paramsArray)
+        {
+            Debug.Assert(paramsArray != null);
+            JsonRpcMethod firstMatch = null;
+            foreach (var m in candidates)
+            {
+                if (!m.AllowExtensionData && paramsArray.Count > m.Parameters.Count) goto NEXT;
+                for (var i = 0; i < m.Parameters.Count; i++)
+                {
+                    var param = m.Parameters[i];
+                    var jparam = i < paramsArray.Count ? paramsArray[i] : null;
+                    if (jparam == null)
+                    {
+                        if (!param.IsOptional) goto NEXT;
+                        else continue;
+                    }
+                    if (!param.MatchJTokenType(jparam.Type)) goto NEXT;
+                }
+                if (firstMatch != null) throw new AmbiguousMatchException();
+                firstMatch = m;
+                NEXT:
+                ;
+            }
+            return firstMatch;
+        }
     }
 }
diff --git a/JsonRpc.Standard/Server/JsonRpcServiceHost.cs b/JsonRpc.Standard/Server/JsonRpcServiceHost.cs
index 83aeba5..e19a597 100644
--- a/JsonRpc.Standard/Server/JsonRpcServiceHost.cs
+++ b/JsonRpc.Standard/Server/JsonRpcServiceHost.cs
@@ -127,12 +127,6 @@ private async Task DispatchRpcMethod(RequestContext context)
             {
                 args = method.UnmarshalArguments(new MarshaledRequest(context.Request, context.CancellationToken));
             }
-            catch (ArgumentException ex)
-            {
-                // Signature not match. This is not likely to happen. Still there might be problem with binder.
-                TrySetErrorResponse(context, JsonRpcErrorCode.InvalidParams, ex.Message);
-                return;
-            }
             catch (Exception ex)
             {
                 TrySetErrorResponse(context, JsonRpcErrorCode.InvalidParams, ex.Message);
diff --git a/UnitTestProject1/ServiceHostTests.cs b/UnitTestProject1/ServiceHostTests.cs
index 14049aa..db139b3 100644
--- a/UnitTestProject1/ServiceHostTests.cs
+++ b/UnitTestProject1/ServiceHostTests.cs
@@ -17,8 +17,7 @@ public class ServiceHostTests : UnitTestBase
         public ServiceHostTests(ITestOutputHelper output) : base(output)
         {
         }
-
-
+        
         [Fact]
         public async Task BasicServiceHostTest()
         {
@@ -50,5 +49,26 @@ public async Task BasicServiceHostTest()
             Assert.Equal(JsonRpcErrorCode.UnhandledClrException, (JsonRpcErrorCode) response.Error.Code);
         }
 
+        [Fact]
+        public async Task InvokeWithPositionalArgumentsTest()
+        {
+            var host = Utility.CreateJsonRpcServiceHost(this);
+            var response = await host.InvokeAsync(
+                new RequestMessage(123, "add", JToken.FromObject(new[] {20, 35})),
+                null,
+                CancellationToken.None);
+            Assert.NotNull(response);
+            Assert.Equal(123, response.Id);
+            Assert.Null(response.Error);
+            Assert.Equal(55, (int)response.Result);
+            response = await host.InvokeAsync(
+                new RequestMessage("TEST", "add", JToken.FromObject(new[] {"abc", "def"})),
+                null,
+                CancellationToken.None);
+            Assert.NotNull(response);
+            Assert.Equal("TEST", response.Id);
+            Assert.Null(response.Error);
+            Assert.Equal("abcdef", (string)response.Result);
+        }
     }
 }