Added repro for a bug

src/Samples/Common/DotVVM.Samples.Common.csproj

@@ -118,6 +118,9 @@
     <None Remove="Views\FeatureSamples\LambdaExpressions\ClientSideFiltering.dothtml" />
     <None Remove="Views\FeatureSamples\LambdaExpressions\LambdaExpressions.dothtml" />
     <None Remove="Views\FeatureSamples\Localization\Globalize.dothtml" />
+    <None Remove="Views\FeatureSamples\MarkupControl\CommandAsProperty.dotcontrol" />
+    <None Remove="Views\FeatureSamples\MarkupControl\CommandAsPropertyPage.dothtml" />
+    <None Remove="Views\FeatureSamples\MarkupControl\CommandAsPropertyWrapper.dotcontrol" />
     <None Remove="Views\FeatureSamples\MarkupControl\MarkupDefinedProperties.dothtml" />
     <None Remove="Views\FeatureSamples\MarkupControl\MarkupDefinedPropertiesControl.dotcontrol" />
     <None Remove="Views\FeatureSamples\MarkupControl\ServiceDependency\ServiceDependencyControl.dotcontrol" />

src/Samples/Common/DotvvmStartup.cs

@@ -267,6 +267,8 @@ private static void AddControls(DotvvmConfiguration config)
             config.Markup.AddCodeControls("cc", typeof(Loader));
             config.Markup.AddMarkupControl("sample", "EmbeddedResourceControls_Button", "embedded://EmbeddedResourceControls/Button.dotcontrol");
             config.Markup.AddMarkupControl("cc", "NodeControl", "Views/ControlSamples/HierarchyRepeater/NodeControl.dotcontrol");
+            config.Markup.AddMarkupControl("cc", "CommandAsProperty", "Views/FeatureSamples/MarkupControl/CommandAsProperty.dotcontrol");
+            config.Markup.AddMarkupControl("cc", "CommandAsPropertyWrapper", "Views/FeatureSamples/MarkupControl/CommandAsPropertyWrapper.dotcontrol");
 
             config.Markup.AutoDiscoverControls(new DefaultControlRegistrationStrategy(config, "sample", "Views/"));
 

src/Samples/Common/ViewModels/FeatureSamples/MarkupControl/CommandAsPropertyPageViewModel.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using DotVVM.Framework.ViewModel;
+using DotVVM.Framework.Hosting;
+
+namespace DotVVM.Samples.Common.ViewModels.FeatureSamples.MarkupControl
+{
+    public class CommandAsPropertyPageViewModel : DotvvmViewModelBase
+    {
+
+        public List<ItemModel> Items { get; set; } = new() {
+            new ItemModel() { Name = "One", IsTrue = true },
+            new ItemModel() { Name = "Two", IsTrue = false },
+            new ItemModel() { Name = "Three", IsTrue = true }
+        };
+
+        public ItemModel SelectedItem { get; set; }
+
+        public Task MyFunction(string name, bool isTrue)
+        {
+            SelectedItem = new ItemModel() { Name = name, IsTrue = isTrue };
+            return Task.CompletedTask;
+        }
+
+
+        public class ItemModel
+        {
+            public string Name { get; set; }
+            public bool IsTrue { get; set; }
+
+        }
+    }
+}
+

src/Samples/Common/Views/FeatureSamples/MarkupControl/CommandAsProperty.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using DotVVM.Framework.Binding;
+using DotVVM.Framework.Controls;
+
+namespace DotVVM.Samples.Common.Views.FeatureSamples.MarkupControl
+{
+    public class CommandAsProperty : DotvvmMarkupControl
+    {
+
+        public Func<string, bool, Task> Click
+        {
+            get => (Func<string, bool, Task>)GetValue(ClickProperty)!;
+            set => SetValue(ClickProperty, value);
+        }
+        public static readonly DotvvmProperty ClickProperty
+                = DotvvmProperty.Register<Func<string, bool, Task>, CommandAsProperty>(c => c.Click, null);
+
+    }
+}
+

src/Samples/Common/Views/FeatureSamples/MarkupControl/CommandAsProperty.dotcontrol

@@ -0,0 +1,10 @@
+@viewModel System.String, mscorlib
+@baseType DotVVM.Samples.Common.Views.FeatureSamples.MarkupControl.CommandAsProperty, DotVVM.Samples.Common
+
+<%-- When uncommented, it produces an error --%>
+<%-- In Release mode, the error that is really hard to debug (maybe it was caused because the control was loaded from embedded resource). --%>
+<%--<dot:Button Text="{value: _this}" Click="{command: _control.Click}" />--%>
+
+
+<%--The following with ToString works somehow and I am not sure by what magic--%>
+<dot:Button Text="{value: _this}" Click="{command: _control.Click.ToString()}" />

src/Samples/Common/Views/FeatureSamples/MarkupControl/CommandAsPropertyPage.dothtml

@@ -0,0 +1,19 @@
+@viewModel DotVVM.Samples.Common.ViewModels.FeatureSamples.MarkupControl.CommandAsPropertyPageViewModel, DotVVM.Samples.Common
+
+<!DOCTYPE html>
+
+<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
+<head>
+    <meta charset="utf-8" />
+    <title></title>
+</head>
+<body>
+
+    <cc:CommandAsPropertyWrapper Click="{command: (string name, bool isTrue) => _root.MyFunction(name, isTrue)}" />
+
+    <p DataContext="{value: SelectedItem}">Selected item: {{value: Name}}, {{value: IsTrue}}</p>
+
+</body>
+</html>
+
+

src/Samples/Common/Views/FeatureSamples/MarkupControl/CommandAsPropertyWrapper.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using DotVVM.Framework.Binding;
+using DotVVM.Framework.Controls;
+
+namespace DotVVM.Samples.Common.Views.FeatureSamples.MarkupControl
+{
+    public class CommandAsPropertyWrapper : DotvvmMarkupControl
+    {
+
+        public Func<string, bool, Task> Click
+        {
+            get { return (Func<string, bool, Task>)GetValue(ClickProperty); }
+            set { SetValue(ClickProperty, value); }
+        }
+        public static readonly DotvvmProperty ClickProperty
+            = DotvvmProperty.Register<Func<string, bool, Task>, CommandAsPropertyWrapper>(c => c.Click, null);
+
+    }
+}
+

src/Samples/Common/Views/FeatureSamples/MarkupControl/CommandAsPropertyWrapper.dotcontrol

@@ -0,0 +1,10 @@
+@viewModel DotVVM.Samples.Common.ViewModels.FeatureSamples.MarkupControl.CommandAsPropertyPageViewModel, DotVVM.Samples.Common
+@baseType DotVVM.Samples.Common.Views.FeatureSamples.MarkupControl.CommandAsPropertyWrapper, DotVVM.Samples.Common
+
+<dot:Repeater DataSource="{value: Items}">
+    <%--
+    The correct syntax would be Click="{value: _control.Click(_parent.Name, _parent.IsTrue)}"
+    Btw is value binding the right thing, or shall we use resource binding here?
+    --%>
+    <cc:CommandAsProperty Click="{value: _control.Click(_parent.Name, _parent.IsTrue)}" DataContext="{value: Name}" />
+</dot:Repeater>