从一个ListBox复制到另一个ListListBoxItem

Question

I have two ListBoxes. I want to copy SelectedItem from the first ListBox into Second one.

Why this code does not work ?

    private void frm_addDispatchBoard2_Load(object sender, EventArgs e)
    {
        using(propertiesManagementDataContext db = new propertiesManagementDataContext())
        {
            var Buildings = db.Buildings.Select(q => new { q.BuildingLandNumber, q.BuildingId });

            listBox_allBuildings.DataSource = Buildings;
            listBox_allBuildings.DisplayMember = "BuildingLandNumber";
            listBox_allBuildings.ValueMember = "BuildingId";
        }          
    }

    private void btn_addBuilding_Click(object sender, EventArgs e)
    {
        if(listBox_allBuildings.SelectedIndex > 0)
        {
            listBox_selectedBuildings.Items.Add(listBox_allBuildings.SelectedItem);            
        }
    }

The result I got:

Answer 1

try this I am not sure why you are looking for a Contains but if you really need that look at the difference between SelectedValue and SelectedItem

Use this code right here as a test to see if the expected value shows up in a MessageBox

string selected = listBox_allBuildings.GetItemText(listBox_allBuildings.SelectedValue);    
MessageBox.Show(selected);

this should help you to see the values in the Listbox on the right

private void btn_addBuilding_Click(object sender, EventArgs e)
{
    if(listBox_allBuildings.SelectedIndex != -1)
    {
       var selected = listBox_allBuildings.GetItemText(listBox_allBuildings.SelectedValue);     
       listBox_selectedBuildings.Items.Add(selected);
    }
}