public void Should_Not_Write_To_Old_DataContext()
{
var vm = new OldDataContextViewModel();
var target = new OldDataContextTest();
var fooBinding = new Binding
{
Path = "Foo",
Mode = BindingMode.TwoWay,
};
var barBinding = new Binding
{
Path = "Bar",
Mode = BindingMode.TwoWay,
};
// Bind Foo and Bar to the VM.
target.Bind(OldDataContextTest.FooProperty, fooBinding);
target.Bind(OldDataContextTest.BarProperty, barBinding);
target.DataContext = vm;
// Make sure the control's Foo and Bar properties are read from the VM
Assert.Equal(1, target.GetValue(OldDataContextTest.FooProperty));
Assert.Equal(2, target.GetValue(OldDataContextTest.BarProperty));
// Set DataContext to null.
target.DataContext = null;
// Foo and Bar are no longer bound so they return 0, their default value.
Assert.Equal(0, target.GetValue(OldDataContextTest.FooProperty));
Assert.Equal(0, target.GetValue(OldDataContextTest.BarProperty));
// The problem was here - DataContext is now null, setting Foo to 0. Bar is bound to
// Foo so Bar also gets set to 0. However the Bar binding still had a reference to
// the VM and so vm.Bar was set to 0 erroneously.
Assert.Equal(1, vm.Foo);
Assert.Equal(2, vm.Bar);
}
public void Should_Not_Write_To_Old_DataContext()
{
var vm = new OldDataContextViewModel();
var target = new OldDataContextTest();
var fooBinding = new XamlBinding
{
SourcePropertyPath = "Foo",
BindingMode = BindingMode.TwoWay,
};
var barBinding = new XamlBinding
{
SourcePropertyPath = "Bar",
BindingMode = BindingMode.TwoWay,
};
// Bind Foo and Bar to the VM.
fooBinding.Bind(target, OldDataContextTest.FooProperty);
barBinding.Bind(target, OldDataContextTest.BarProperty);
target.DataContext = vm;
// Make sure the control's Foo and Bar properties are read from the VM
Assert.Equal(1, target.GetValue(OldDataContextTest.FooProperty));
Assert.Equal(2, target.GetValue(OldDataContextTest.BarProperty));
// Set DataContext to null.
target.DataContext = null;
// Foo and Bar are no longer bound so they return 0, their default value.
Assert.Equal(0, target.GetValue(OldDataContextTest.FooProperty));
Assert.Equal(0, target.GetValue(OldDataContextTest.BarProperty));
// The problem was here - DataContext is now null, setting Foo to 0. Bar is bound to
// Foo so Bar also gets set to 0. However the Bar binding still had a reference to
// the VM and so vm.Bar was set to 0 erroneously.
Assert.Equal(1, vm.Foo);
Assert.Equal(2, vm.Bar);
}
