Modified SetCommand to allow avoiding explicit type parameter when using an

Android CheckBox and the default CheckedChange event.

GalaSoft.MvvmLight/GalaSoft.MvvmLight.Platform (Android)/Helpers/Extensions.cs

@@ -272,15 +272,7 @@ namespace GalaSoft.MvvmLight.Helpers
 
             var castedBinding = (Binding<T, T>)commandParameterBinding;
 
-            EventHandler handler = (s, args) =>
-            {
-                var param = castedBinding == null ? default(T) : castedBinding.Value;
-
-                if (command.CanExecute(param))
-                {
-                    command.Execute(param);
-                }
-            };
+            var handler = e.GetCommandHandler(eventName, t, command, castedBinding);
 
             e.AddEventHandler(
                 element,
@@ -378,13 +370,7 @@ namespace GalaSoft.MvvmLight.Helpers
             var t = element.GetType();
             var e = t.GetEventInfoForControl(eventName);
 
-            EventHandler handler = (s, args) =>
-            {
-                if (command.CanExecute(null))
-                {
-                    command.Execute(null);
-                }
-            };
+            var handler = e.GetCommandHandler(eventName, t, command);
 
             e.AddEventHandler(
                 element,
@@ -460,13 +446,7 @@ namespace GalaSoft.MvvmLight.Helpers
             var t = element.GetType();
             var e = t.GetEventInfoForControl(eventName);
 
-            EventHandler handler = (s, args) =>
-            {
-                if (command.CanExecute(commandParameter))
-                {
-                    command.Execute(commandParameter);
-                }
-            };
+            var handler = e.GetCommandHandler(eventName, t, command, commandParameter);
 
             e.AddEventHandler(
                 element,

GalaSoft.MvvmLight/GalaSoft.MvvmLight.Platform (Android)/Helpers/ExtensionsAndroid.cs

@@ -16,8 +16,11 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Reflection;
+using System.Windows.Input;
 using Android.Views;
 using Android.Widget;
+using GalaSoft.MvvmLight.Command;
 
 namespace GalaSoft.MvvmLight.Helpers
 {
@@ -84,5 +87,100 @@ namespace GalaSoft.MvvmLight.Helpers
 
             return eventName;
         }
+
+        internal static Delegate GetCommandHandler(
+            this EventInfo info,
+            string eventName, 
+            Type elementType, 
+            ICommand command)
+        {
+            Delegate result;
+
+            if (string.IsNullOrEmpty(eventName)
+                && elementType == typeof (CheckBox))
+            {
+                EventHandler<CompoundButton.CheckedChangeEventArgs> handler = (s, args) =>
+                {
+                    if (command.CanExecute(null))
+                    {
+                        command.Execute(null);
+                    }
+                };
+
+                result = handler;
+            }
+            else
+            {
+                EventHandler handler = (s, args) =>
+                {
+                    if (command.CanExecute(null))
+                    {
+                        command.Execute(null);
+                    }
+                };
+
+                result = handler;
+            }
+
+            return result;
+        }
+
+        internal static Delegate GetCommandHandler<T>(
+            this EventInfo info,
+            string eventName,
+            Type elementType,
+            RelayCommand<T> command,
+            Binding<T, T> castedBinding)
+        {
+            Delegate result;
+
+            if (string.IsNullOrEmpty(eventName)
+                && elementType == typeof(CheckBox))
+            {
+                EventHandler<CompoundButton.CheckedChangeEventArgs> handler = (s, args) =>
+                {
+                    var param = castedBinding == null ? default(T) : castedBinding.Value;
+                    command.Execute(param);
+                };
+
+                result = handler;
+            }
+            else
+            {
+                EventHandler handler = (s, args) =>
+                {
+                    var param = castedBinding == null ? default(T) : castedBinding.Value;
+                    command.Execute(param);
+                };
+
+                result = handler;
+            }
+
+            return result;
+        }
+
+        internal static Delegate GetCommandHandler<T>(
+            this EventInfo info,
+            string eventName,
+            Type elementType,
+            RelayCommand<T> command,
+            T commandParameter)
+        {
+            Delegate result;
+
+            if (string.IsNullOrEmpty(eventName)
+                && elementType == typeof(CheckBox))
+            {
+                EventHandler<CompoundButton.CheckedChangeEventArgs> handler = (s, args) => command.Execute(commandParameter);
+                result = handler;
+            }
+            else
+            {
+                EventHandler handler = (s, args) => command.Execute(commandParameter);
+                result = handler;
+            }
+
+            return result;
+        }
     }
 }

GalaSoft.MvvmLight/GalaSoft.MvvmLight.Platform (iOS)/Helpers/ExtensionsApple.cs

@@ -16,7 +16,10 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Reflection;
+using System.Windows.Input;
 using Foundation;
+using GalaSoft.MvvmLight.Command;
 using UIKit;
 
 namespace GalaSoft.MvvmLight.Helpers
@@ -349,5 +352,59 @@ namespace GalaSoft.MvvmLight.Helpers
 
             return eventName;
         }
+
+
+        internal static Delegate GetCommandHandler(
+            this EventInfo info,
+            string eventName,
+            Type elementType,
+            ICommand command)
+        {
+            // At the moment, all supported controls with default events
+            // in iOS are using EventHandler, and not EventHandler<...>.
+
+            EventHandler handler = (s, args) =>
+            {
+                if (command.CanExecute(null))
+                {
+                    command.Execute(null);
+                }
+            };
+
+            return handler;
+        }
+
+        internal static Delegate GetCommandHandler<T>(
+            this EventInfo info,
+            string eventName,
+            Type elementType,
+            RelayCommand<T> command,
+            Binding<T, T> castedBinding)
+        {
+            // At the moment, all supported controls with default events
+            // in iOS are using EventHandler, and not EventHandler<...>.
+
+            EventHandler handler = (s, args) =>
+            {
+                var param = castedBinding == null ? default(T) : castedBinding.Value;
+                command.Execute(param);
+            };
+
+            return handler;
+        }
+
+        internal static Delegate GetCommandHandler<T>(
+            this EventInfo info,
+            string eventName,
+            Type elementType,
+            RelayCommand<T> command,
+            T commandParameter)
+        {
+            // At the moment, all supported controls with default events
+            // in iOS are using EventHandler, and not EventHandler<...>.
+
+            EventHandler handler = (s, args) => command.Execute(commandParameter);
+            return handler;
+        }
     }
 }

GalaSoft.MvvmLight/Tests/AndroidTestApp/Binding/SetCommandTest.cs

@@ -207,7 +207,7 @@ namespace GalaSoft.MvvmLight.Test.Binding
         }
 
         [Test]
-        public void SetCommand_OnCheckBoxNoValueNoEventName_ClickEventShouldBeUsed()
+        public void SetCommand_OnCheckBoxNoValueNoEventName_CheckedChangeEventShouldBeUsed()
         {
             var value = DateTime.Now.Ticks.ToString();
             var vmTarget = new TestViewModel();
@@ -215,7 +215,7 @@ namespace GalaSoft.MvvmLight.Test.Binding
 
             var checkBox = new CheckBox(Application.Context);
 
-            checkBox.SetCommand<CompoundButton.CheckedChangeEventArgs>(vmTarget.SetPropertyWithoutValueCommand);
+            checkBox.SetCommand(vmTarget.SetPropertyWithoutValueCommand);
 
             Assert.IsNull(vmTarget.TargetProperty);
             checkBox.PerformClick();
@@ -279,7 +279,7 @@ namespace GalaSoft.MvvmLight.Test.Binding
                 vmSource,
                 () => vmSource.Model.MyProperty);
 
-            checkBox.SetCommand<string, CompoundButton.CheckedChangeEventArgs>(
+            checkBox.SetCommand(
                 vmTarget.SetPropertyCommand,
                 _binding);
 
@@ -319,7 +319,7 @@ namespace GalaSoft.MvvmLight.Test.Binding
 
             var checkBox = new CheckBox(Application.Context);
 
-            checkBox.SetCommand<string, CompoundButton.CheckedChangeEventArgs>(
+            checkBox.SetCommand(
                 vmTarget.SetPropertyCommand,
                 value);
 
@@ -379,7 +379,7 @@ namespace GalaSoft.MvvmLight.Test.Binding
             var vmTarget = new TestViewModel();
             var checkBox = new CheckBox(Application.Context);
 
-            checkBox.SetCommand<CompoundButton.CheckedChangeEventArgs>(vmTarget.TestCommandImpl);
+            checkBox.SetCommand(vmTarget.TestCommandImpl);
 
             var castedCommand = (CommandImpl)vmTarget.TestCommandImpl;