diff --git a/Esiur/Core/AsyncChunk.cs b/Esiur/Core/AsyncChunk.cs
deleted file mode 100644
index 6e04fb4..0000000
--- a/Esiur/Core/AsyncChunk.cs
+++ /dev/null
@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Esiur.Core
-{
-    // This interface is used to provide return type for templates and support chunk callbacks using IAsyncEnumerable feature of C# 8
-    public interface IAsyncChunk<T> : IAsyncEnumerable<object>
-    {
-
-    }
-}
diff --git a/Esiur/Core/InvocationContext.cs b/Esiur/Core/InvocationContext.cs
index 6ad6090..0118f8f 100644
--- a/Esiur/Core/InvocationContext.cs
+++ b/Esiur/Core/InvocationContext.cs
@@ -9,13 +9,22 @@ namespace Esiur.Core
     {
         private uint CallbackId;
 
+        internal bool Ended;
+
         public void Chunk(object value)
         {
+            if (Ended)
+                throw new Exception("Execution has ended.");
 
+            Connection.SendChunk(CallbackId, value);
         }
 
-        public void Progress(int value) { 
+        public void Progress(int value, int max) {
 
+            if (Ended)
+                throw new Exception("Execution has ended.");
+
+            Connection.SendProgress(CallbackId, value, max);
         }
 
         public DistributedConnection Connection { get; internal set; }
diff --git a/Esiur/Net/IIP/DistributedConnectionProtocol.cs b/Esiur/Net/IIP/DistributedConnectionProtocol.cs
index 7b76626..e505527 100644
--- a/Esiur/Net/IIP/DistributedConnectionProtocol.cs
+++ b/Esiur/Net/IIP/DistributedConnectionProtocol.cs
@@ -268,7 +268,7 @@ partial class DistributedConnection
                         .Done();
     }
 
-    void SendProgress(uint callbackId, int value, int max)
+    internal void SendProgress(uint callbackId, int value, int max)
     {
         SendParams()
             .AddUInt8((byte)(0xC0 | (byte)IIPPacketReport.ProgressReport))
@@ -279,7 +279,7 @@ partial class DistributedConnection
         //SendParams(, callbackId, value, max);
     }
 
-    void SendChunk(uint callbackId, object chunk)
+    internal void SendChunk(uint callbackId, object chunk)
     {
         var c = Codec.Compose(chunk, this);
         SendParams()
@@ -353,7 +353,7 @@ partial class DistributedConnection
                 attachedResources.Remove(resourceId);
             }
 
-            
+
         }
         else if (neededResources.Contains(resourceId))
         {
@@ -1472,6 +1472,8 @@ partial class DistributedConnection
 
         object[] args = new object[pis.Length];
 
+        InvocationContext context = null;
+
         if (pis.Length > 0)
         {
             if (pis.Last().ParameterType == typeof(DistributedConnection))
@@ -1480,16 +1482,33 @@ partial class DistributedConnection
                 {
                     if (arguments.ContainsKey(i))
                         args[i] = DC.CastConvert(arguments[i], pis[i].ParameterType);
-                    else if (ft.Arguments[i].Type.Nullable)// Nullable.GetUnderlyingType(pis[i].ParameterType) != null)
+                    else if (ft.Arguments[i].Type.Nullable)
                         args[i] = null;
                     else
                         args[i] = Type.Missing;
 
                 }
-                //args[i] = arguments.ContainsKey(i) ?
-                //                DC.CastConvert(arguments[i], pis[i].ParameterType) : Type.Missing;
+
                 args[args.Length - 1] = this;
             }
+            else if (pis.Last().ParameterType == typeof(InvocationContext))
+            {
+                context = new InvocationContext(this, callback);
+
+                for (byte i = 0; i < pis.Length - 1; i++)
+                {
+                    if (arguments.ContainsKey(i))
+                        args[i] = DC.CastConvert(arguments[i], pis[i].ParameterType);
+                    else if (ft.Arguments[i].Type.Nullable)
+                        args[i] = null;
+                    else
+                        args[i] = Type.Missing;
+
+                }
+
+                args[args.Length - 1] = context;
+
+            }
             else
             {
                 for (byte i = 0; i < pis.Length; i++)
@@ -1509,6 +1528,7 @@ partial class DistributedConnection
         try
         {
             rt = ft.MethodInfo.Invoke(target, args);
+            context.Ended = true;
         }
         catch (Exception ex)
         {
diff --git a/Esiur/Resource/ExportAttribute.cs b/Esiur/Resource/ExportAttribute.cs
index c7fa916..c2a983b 100644
--- a/Esiur/Resource/ExportAttribute.cs
+++ b/Esiur/Resource/ExportAttribute.cs
@@ -10,7 +10,6 @@ namespace Esiur.Resource;
 public class ExportAttribute : Attribute
 {
     public string Name { get; private set; } = null;
-    public Type ReturnType { get; private set; } = null;
 
     public ExportAttribute()
     {
@@ -22,16 +21,4 @@ public class ExportAttribute : Attribute
         Name = name;
     }
 
-    public ExportAttribute(Type returnType)
-    {
-        ReturnType = returnType;
-    }
-
-    public ExportAttribute(string name, Type returnType)
-    {
-        Name = name;
-        ReturnType = returnType;
-    }
-
-
 }
diff --git a/Esiur/Resource/Template/FunctionTemplate.cs b/Esiur/Resource/Template/FunctionTemplate.cs
index 981f6c7..0538eeb 100644
--- a/Esiur/Resource/Template/FunctionTemplate.cs
+++ b/Esiur/Resource/Template/FunctionTemplate.cs
@@ -91,17 +91,13 @@ public class FunctionTemplate : MemberTemplate
         else if (genericRtType == typeof(IEnumerable<>) || genericRtType == typeof(IAsyncEnumerable<>))
         {
             // get export
-            rtType = RepresentationType.FromType(mi.GetCustomAttribute<ExportAttribute>()?.ReturnType ?? typeof(object));
+            rtType = RepresentationType.FromType(mi.ReturnType.GetGenericArguments()[0]);
         }
         else
         {
             rtType = RepresentationType.FromType(mi.ReturnType);
         }
 
-        //var rtType = genericRtType == typeof(AsyncReply<>) ?
-        //        RepresentationType.FromType(mi.ReturnType.GetGenericArguments()[0]) :
-        //        RepresentationType.FromType(mi.ReturnType);
-
         if (rtType == null)
             throw new Exception($"Unsupported type `{mi.ReturnType}` in method `{type.Name}.{mi.Name}` return");