Databinding to nested property - Cannot bind property or column (Winforms)

问题

We are running a .NET 4.0 application using Windows Forms. The application uses a single form for two different types of objects.

namespace NetIssue
{
    public partial class Form1 : Form
    {
        B myObj;
        public Form1()
        {
            InitializeComponent();

            myObj = new B();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            textBox1.DataBindings.Add(new Binding("Text", myObj, "c.Message"));
        }
    }

    public class Comment {
        public int ID { get; set; }
        public string Message { get; set; }

        public Comment(string msg)
        {
            Message = msg;
        }
    }

    public class A {
        string MyName = "";
    }

    public class B : A {
        public Comment c { get; set; }

        public B()
        {
            c = new Comment("test");
        }
    }
}

When the binding above is run in .NET 4.0, we get the error

An error occured: Cannot bind to the property or column Message on the DataSource. Parameter name: dataMember

However, if we install .NET 4.5 this error goes away.

Is this a limitation of .NET 4.0, a bug in .NET 4.0, or is something else going on?

回答1:

Short story: Windows Forms data binding doesn't support property path, that's why you are getting the error.

Well, this is what I was thinking until today. But trying your code I was surprised that it indeed works on .NET 4.5 machine! So looks like MS has added that at some point - to be honest, have no idea when. But it's there now! Anyway, if backward compatibility is a concern, one should avoid using that feature (although it would be quite pity).

回答2:

You can use either of these options:

B myObj = new B();
textBox1.DataBindings.Add(new Binding("Text", ((B)myObj).c, "Message"));

var bs = new BindingSource(myObj, null);
textBox1.DataBindings.Add("Text", bs, "c.Message");

textBox1.DataBindings.Add("Text", new B[] { myObj }, "c.Message");

来源：https://stackoverflow.com/questions/33789575/databinding-to-nested-property-cannot-bind-property-or-column-winforms

标签

.net

winforms

data-binding

.net-4.0