InvalidOperationException - A TwoWay or OneWayToSource binding cannot work on the read-only property

Question

I'm using the MVVM pattern and am receiving the following when i run my app

InvalidOperationException A TwoWay or OneWayToSource binding cannot work on the read-only property 'Options' of type 'ViewModel.SynergyViewModel'.

I have commented all my source out in my view model and have traced this back to a check box. If i comment out the the checkbox or the properity in my view model the app runs, minus the functionality. Below i have listed the code for my checkbox and the property within the viewmodel.

<CheckBox Grid.Column="4" HorizontalAlignment="Right" Margin="5,0,5,5" IsChecked="{Binding Options}" Content="Options"/>

private bool _Options;
public bool Options
{
    get
    {
        return _Options;
    }
    private set
    {
        if (_Options == value)
            return;

        _Options = value;
        OnPropertyChanged("Options");
    }
}

System.InvalidOperationException occurred Message=A TwoWay or OneWayToSource binding cannot work on the read-only property 'Options' of type 'ViewModel.MyViewModel'. Source=PresentationFramework StackTrace: at MS.Internal.Data.PropertyPathWorker.CheckReadOnly(Object item, Object info) InnerException:

Any ideas on what i'm what i'm missing here?

Solution 1

Either make your setter public or explicitly set the Binding.Mode to OneWay.

Solution 2

Your setter is private, either specify the binding to be mode OneWay or remove the private from the setter

Comments

[Jordan]

If you're developing a .net 4.0 WPF project on a machine with .net 4.5 installed, you will not run into this error during development! Microsoft needs to fix this.

[Omaer]

It's so strange that I'm getting the same error with an internal setter... I would have assumed an internal setter would be allowed, but strangely not.

[user0474975]

I wish this answer specified HOW to set the Binding.Mode to OneWay - where do I do this? In the set?

[dibs487]

IsChecked="{Binding Options, Mode=OneWay}"