Hello:

I have a question regarding databinding and a ComboBox. I have a class called "Person." Each person has a sibling, and this is wrapped in a property of the class. Now for the UI. I have a form with two controls: a ListBox control and a ComboBox control. The ListBox is just a list of "Person" and ComboBox is a list of "Person" too.

Overall, what I'm trying toaccomplish is thata user canselect a "Person" in the ListBox. Once selected, the user can select another "Person" in the combobox, identifying that Person's sibling. Note: I don't care about error checking such as John being John's own sibling. It's pretty simple.

Here's thecode...

public partial class Form1 : Form
    {
        private void Form1_Load(object sender, EventArgs e)
        {
            List<Person> lstPersons = new List<Person>();
            Person person1 = new Person("John");
            Person person2 = new Person("Betty");
            
            Person person3 = new Person("Gary");
            Person person4 = new Person("Susan");

            person1.Sibling = person2;  // John is Betty's sibling and vice versa
            person2.Sibling = person1;

            person3.Sibling = person4;  // Gary is Susan's sibling and vice versa
            person4.Sibling = person3;

            lstPersons.AddRange(new Person[] { person1, person2, person3, person4 });

            BindingSource bs = new BindingSource();
            bs.DataSource = lstPersons;

            BindingSource bs2 = new BindingSource();
            bs2.DataSource = lstPersons;

            this.listBox1.DataSource = bs;
            this.comboBox1.DataSource = bs2;

            this.comboBox1.DataBindings.Add("SelectedItem", bs, "Sibling", true, DataSourceUpdateMode.OnValidation);
        }

        public class Person
        {
            private readonly string _Name;
            private Person _Sibling = null;

            public Person(string Name)
            {
                this._Name = Name;
            }

            public override string ToString()
            {
                return this._Name;
            }

            public Person Sibling
            {
                get
                {
                    return _Sibling;
                }
                set
                {
                    this._Sibling = value;
                }
            }
        }

Here's my question. If I select a person in the ListBox, the ComboBox will reflect the person's sibling. Now, without changing the sibling in the ComboBox, I select another person from the ListBox. What happens is thatSET on the Person's SIBLINGproperty is called when, in fact, I didn't change the sibling. Why is the SET property being called everytime I select a new user in the ListBox? Is there a way to prevent this from happening and ONLY call set when I actually do change the person's sibling?

Thank you.


Trecius

This is because they use the same BindingManagerBases instances.

Please see the following article. It tells about Control Synchronization.

http://windowsclient.net/blogs/faqs/archive/2006/07/12/what-is-bindingcontext.aspx

In your code:

· -> this.comboBox1.DataBindings.Add("SelectedItem", bs, "Sibling", true, DataSourceUpdateMode.OnValidation);

Change “bs�to “bs2�will be ok.

Best regards,

Ling Wang

This is because they use the same BindingManagerBases instances.

Please see the following article. It tells about Control Synchronization.

http://windowsclient.net/blogs/faqs/archive/2006/07/12/what-is-bindingcontext.aspx

In your code:

· -> this.comboBox1.DataBindings.Add("SelectedItem", bs, "Sibling", true, DataSourceUpdateMode.OnValidation);

Change “bs�to “bs2�will be ok.

Best regards,

Ling Wang