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Shael Shah
50
Binding expression errors when using AlternateBinding
posted

Hello, 

In our application we have a XamDataGrid with dynamic nested columns. We've set up the backing data classes as the following: 

    class Parent
    {
            public Parent(string name)
            {
                Name = name;
            }

            public string Name { get; set; }

            public List<Child> Children { get; set; } = new List<Child>();
    }

    class Child
    {
            public string Name { get; set; }
    }

and we setup the fields like the following:

            var unboundField = new Field()
            {
                     BindingType = BindingType.UseAlternateBinding,
                    AlternateBinding = new Binding()
                    {
                        Path = new PropertyPath("Parents[parentIndex].Children[{childIndex}].[{property.PropertyName}]")
                    }
            };

and then the data is created the following way:

        public VM()
        {
                var p1 = new Parent();
                var p2 = new Parent();

                var c1 = new Child();
                var c2 = new Child();

                var children = new List<Child>() { c1, c2 };

                p1.Children = children;

                Parents = new List<Parent>() { p1, p2 };
        }

I want to display a column for the parents name and then a column for each child object in the list of Parent.Children

The issue comes from the alternatebinding string because it's essentially hardcoded - if the children property of parent is an empty list (a valid use case) then trying to access the property of the child object causes an exception. Is there a way to check for the contents of the children list when fetching the value?

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