diff --git a/sandbox/WpfApp1/MainWindow.xaml b/sandbox/WpfApp1/MainWindow.xaml
index e0563c71..4925d71d 100644
--- a/sandbox/WpfApp1/MainWindow.xaml
+++ b/sandbox/WpfApp1/MainWindow.xaml
@@ -7,17 +7,21 @@
         mc:Ignorable="d"
         Title="MainWindow" Height="450" Width="800">
     <Window.DataContext>
-        <!--<local:BasicUsagesViewModel />-->
-        <!--<local:ValidationViewModel />-->
-        <local:CommandViewModel />
+        <local:BasicUsagesViewModel />
+        <!--<local:ValidationViewModel />
+        <local:CommandViewModel />-->
     </Window.DataContext>
-    <!--<StackPanel>
+    <StackPanel>
         <TextBlock Text="Basic usages" FontSize="24" />
         <Label Content="Input" />
         <TextBox Text="{Binding Input.Value, UpdateSourceTrigger=PropertyChanged}" />
-        <Label Content="Output" />
+        <Label Content="BindableReactiveProperty.Value" />
         <TextBlock Text="{Binding Output.Value}" />
-    </StackPanel>-->
+        <Label Content="ReadOnlyBindableReactiveProperty.CurrentValue" />
+        <TextBlock Text="{Binding OutputRO.CurrentValue}" />
+        <TextBlock Text="{Binding OutputRO2.CurrentValue}" />
+        <Button Content="add" Command="{Binding AddCommand}" />
+    </StackPanel>
 
     <!--<StackPanel Margin="10">
         <Label Content="Validation" />
@@ -28,9 +32,9 @@
     </StackPanel>-->
 
 
-    <StackPanel Margin="10">
+    <!--<StackPanel Margin="10">
         <Label Content="Command" />
         <CheckBox IsChecked="{Binding OnCheck.Value}" />
         <Button Content="Btn" Command="{Binding ShowMessageBox}" />
-    </StackPanel>
+    </StackPanel>-->
 </Window>
diff --git a/sandbox/WpfApp1/MainWindow.xaml.cs b/sandbox/WpfApp1/MainWindow.xaml.cs
index e34bf45a..9e117ffb 100644
--- a/sandbox/WpfApp1/MainWindow.xaml.cs
+++ b/sandbox/WpfApp1/MainWindow.xaml.cs
@@ -59,11 +59,26 @@ public class BasicUsagesViewModel : IDisposable
 {
     public BindableReactiveProperty<string> Input { get; }
     public BindableReactiveProperty<string> Output { get; }
+    public ReadOnlyBindableReactiveProperty<string> OutputRO { get; }
+    public ReadOnlyBindableReactiveProperty<string> OutputRO2 { get; }
+    public ReactiveCommand<Unit> AddCommand { get; } = new();
 
     public BasicUsagesViewModel()
     {
         Input = new BindableReactiveProperty<string>("");
         Output = Input.Select(x => x.ToUpper()).ToBindableReactiveProperty("");
+        var rrp = Input.ToReadOnlyReactiveProperty("");
+        OutputRO = Input.ToReadOnlyBindableReactiveProperty("");
+        OutputRO2 = rrp.ToReadOnlyBindableReactiveProperty("");
+        AddCommand.SubscribeAwait(async (_, _) =>
+        {
+            var i = 0;
+            while (i++ < 10)
+            {
+                Input.Value += "@";
+                await Task.Delay(500);
+            }
+        });
     }
 
     public void Dispose()
diff --git a/src/R3/BindableReactiveProperty.cs b/src/R3/BindableReactiveProperty.cs
index 4eb29fe2..1fef92ee 100644
--- a/src/R3/BindableReactiveProperty.cs
+++ b/src/R3/BindableReactiveProperty.cs
@@ -42,6 +42,7 @@ public ReadOnlyBindableReactiveProperty(T value, IEqualityComparer<T>? equalityC
 public class BindableReactiveProperty<T> : ReadOnlyBindableReactiveProperty<T>, INotifyPropertyChanged, INotifyDataErrorInfo, IBindableReactiveProperty
 {
     IDisposable? subscription;
+    bool isReadOnly = false;
 
     public T Value
     {
@@ -82,7 +83,11 @@ public BindableReactiveProperty(T value, IEqualityComparer<T>? equalityComparer)
     {
     }
 
-    // ToBindableReactiveProperty
+    public BindableReactiveProperty(T value, IEqualityComparer<T>? equalityComparer, bool isReadOnly)
+    : base(value, equalityComparer)
+    {
+        this.isReadOnly = isReadOnly;
+    }
 
     internal BindableReactiveProperty(Observable<T> source, T initialValue, IEqualityComparer<T>? equalityComparer)
         : base(initialValue, equalityComparer)
@@ -90,6 +95,14 @@ internal BindableReactiveProperty(Observable<T> source, T initialValue, IEqualit
         this.subscription = source.Subscribe(new Observer(this));
     }
 
+    // ToBindableReactiveProperty
+
+    public ReadOnlyBindableReactiveProperty<T> ToReadOnlyBindableReactiveProperty(T initialValue = default!)
+    {
+        isReadOnly = true;
+        return this;
+    }
+
     protected override void DisposeCore()
     {
         subscription?.Dispose();
@@ -131,7 +144,7 @@ protected override void OnValueChanged(T value)
 
                 if (!validationContext.TryValidateValue(value, errors))
                 {
-                    ErrorsChanged?.Invoke(this, ValueChangedEventArgs.DataErrorsChanged);
+                    ErrorsChanged?.Invoke(this, ValueChangedEventArgs.GetDataErrorsChangedEventArgs(isReadOnly));
 
                     // set is completed(validation does not call before set) so continue call PropertyChanged
                 }
@@ -150,12 +163,12 @@ protected override void OnValueChanged(T value)
                 if (errors != null && errors.Count != 0)
                 {
                     errors.Clear();
-                    ErrorsChanged?.Invoke(this, ValueChangedEventArgs.DataErrorsChanged);
+                    ErrorsChanged?.Invoke(this, ValueChangedEventArgs.GetDataErrorsChangedEventArgs(isReadOnly));
                 }
             }
         }
 
-        PropertyChanged?.Invoke(this, ValueChangedEventArgs.PropertyChanged);
+        PropertyChanged?.Invoke(this, ValueChangedEventArgs.GetPropertyChangedEventArgs(isReadOnly));
     }
 
     // for INotifyDataErrorInfo
@@ -213,7 +226,7 @@ protected override void OnReceiveError(Exception exception)
             errors.Add(new ValidationResult(exception.Message));
         }
 
-        ErrorsChanged?.Invoke(this, ValueChangedEventArgs.DataErrorsChanged);
+        ErrorsChanged?.Invoke(this, ValueChangedEventArgs.GetDataErrorsChangedEventArgs(isReadOnly));
     }
 
     public BindableReactiveProperty<T> EnableValidation()
@@ -302,6 +315,11 @@ public bool TryValidateValue(object? value, ICollection<ValidationResult> valida
 
 internal static class ValueChangedEventArgs
 {
-    internal static readonly PropertyChangedEventArgs PropertyChanged = new PropertyChangedEventArgs("Value");
-    internal static readonly DataErrorsChangedEventArgs DataErrorsChanged = new DataErrorsChangedEventArgs("Value");
+    static readonly PropertyChangedEventArgs propertyChanged = new PropertyChangedEventArgs("Value");
+    static readonly PropertyChangedEventArgs propertyChangedReadOnly = new PropertyChangedEventArgs("CurrentValue");
+    static readonly DataErrorsChangedEventArgs dataErrorsChanged = new DataErrorsChangedEventArgs("Value");
+    static readonly DataErrorsChangedEventArgs dataErrorsChangedReadOnly = new DataErrorsChangedEventArgs("CurrentValue");
+
+    internal static PropertyChangedEventArgs GetPropertyChangedEventArgs(bool isReadOnly) => isReadOnly ? propertyChangedReadOnly : propertyChanged;
+    internal static DataErrorsChangedEventArgs GetDataErrorsChangedEventArgs(bool isReadOnly) => isReadOnly ? dataErrorsChangedReadOnly : dataErrorsChanged;
 }
diff --git a/src/R3/ReactivePropertyExtensions.cs b/src/R3/ReactivePropertyExtensions.cs
index 3e115aa9..1701b2df 100644
--- a/src/R3/ReactivePropertyExtensions.cs
+++ b/src/R3/ReactivePropertyExtensions.cs
@@ -32,21 +32,13 @@ public static BindableReactiveProperty<T> ToBindableReactiveProperty<T>(this Obs
 
     public static ReadOnlyBindableReactiveProperty<T> ToReadOnlyBindableReactiveProperty<T>(this Observable<T> source, T initialValue = default!)
     {
-        if (source is ReadOnlyBindableReactiveProperty<T> rrp)
-        {
-            return rrp;
-        }
         return source.ToReadOnlyBindableReactiveProperty(EqualityComparer<T>.Default, initialValue);
     }
 
     public static ReadOnlyBindableReactiveProperty<T> ToReadOnlyBindableReactiveProperty<T>(this Observable<T> source, IEqualityComparer<T>? equalityComparer, T initialValue = default!)
     {
-        if (source is ReadOnlyBindableReactiveProperty<T> rrp)
-        {
-            return rrp;
-        }
-        // allow to cast ReactiveProperty<T>
-        return new ConnectedBindableReactiveProperty<T>(source, initialValue, equalityComparer);
+        // allow to cast BindableReactiveProperty<T>
+        return new ConnectedBindableReactiveProperty<T>(source, initialValue, equalityComparer, isReadOnly: true);
     }
 }
 
@@ -88,8 +80,8 @@ internal sealed class ConnectedBindableReactiveProperty<T> : BindableReactivePro
 {
     readonly IDisposable sourceSubscription;
 
-    public ConnectedBindableReactiveProperty(Observable<T> source, T initialValue, IEqualityComparer<T>? equalityComparer)
-        : base(initialValue, equalityComparer)
+    public ConnectedBindableReactiveProperty(Observable<T> source, T initialValue, IEqualityComparer<T>? equalityComparer, bool isReadOnly = false)
+        : base(initialValue, equalityComparer, isReadOnly)
     {
         this.sourceSubscription = source.Subscribe(new Observer(this));
     }