Question

Form有一个Combobox和一个ListBox。单击“添加”按钮时，我想将选定的项目从ComboBox添加到ListBox。

public partial class MyForm:Form
{
    List<MyData> data = new List<MyData>();
    private void ShowData()
    {
       listBox1.DataSource = data;
       listBox1.DisplayMember = "Name";
       listBox1.ValueMember = "Id";
    }

    private void buttonAddData_Click(object sender, EventArgs e)
    {
       var selection = (MyData)comboBox1.SelectedItem;
       data.Add(selection);
       ShowData();
    }
}

通过此示例，所选项目将替换为ListBox中的新选择。我需要将项目添加到列表中。

我的代码出了什么问题？

Answer 1

listbox1.DataSource属性查找值更改，但是通过始终指定相同的列表，值不会真正更改。

您可以使用BindingList<T>代替List<T>来自动识别添加的新项目。您的ShowData（）方法必须在启动时调用一次。

public partial class MyForm:Form
{
    public MyForm(){
        InitializeComponent();
        ShowData();
    }

    BindingList<MyData> data = new BindingList<MyData>();

    private void ShowData()
    {
       listBox1.DataSource = data;
       listBox1.DisplayMember = "Name";
       listBox1.ValueMember = "Id";
    }

    private void buttonAddData_Click(object sender, EventArgs e)
    {
       var selection = (MyData)comboBox1.SelectedItem;
       data.Add(selection);
    }
}

Answer 2

我建议使用BindingSource，因为它会正确更新连接的控件。

public partial class MyForm : Form
{
    List<MyData> data = new List<MyData>();
    BindingSource bs = new BindingSource();

    public MyForm()
    {
        IntializeComponents();
        bs.DataSource = data;

       listBox1.DisplayMember = "Name";
       listBox1.ValueMember = "Id";
       listBox1.DataSource = bs;
    }

    private void buttonAddData_Click(object sender, EventArgs e)
    {
       var selection = (MyData)comboBox1.SelectedItem;
       data.Add(selection);

       bs.ResetBindings(false);
    }
}

在飞行中更改控件数据源有时会产生奇怪的结果。

Answer 3

列表框未检测到您更改了DataSource。它只会在Datasource发生更改时刷新，因此请先将DataSource设置为null：

listBox1.DataSource = null;
listBox1.DataSource = data;

您也可以清除这些项目，然后再次设置DataSource：

listBox1.Items.Clear();
listBox1.DataSource = data;

Answer 4

或者，可能最正确的方法是使用提供的ObservableCollection<T>。它的设计目的仅仅是实现INotifyCollectionChanged。

public partial class MyForm : Form
{
    ObservableCollection<MyData> data = new ObservableCollection<MyData>();

    public MyForm()
    {
        listBox1.DataSource = data;
        listBox1.DisplayMember = "Name";
        listBox1.ValueMember = "Id";
    }

    private void buttonAddData_Click(object sender, EventArgs e)
    {
       var selection = (MyData)comboBox1.SelectedItem;
       data.Add(selection);
    }
}

因为ObservableCollection<T>实现了INotifyCollectionChanged，所以只要数据发生变化，DataSource绑定就会自动更新ListBox。

Answer 5

在表单初始化时调用ShowData()以在初始化

上填充列表框

 public Department()
        {
            InitializeComponent();
            ShowData();
        }

ShowData()方法，设置BindingSource，DisplayMember和ValueMember

private void ShowData()
            {
                using (var uow = new UnitOfWork(new SellContext()))
                {
                    listBox1.DataSource = uow.Departments.GetAll().ToList();
                    listBox1.DisplayMember = "DepartmentName";
                    listBox1.ValueMember = "DepartmentId"; 
                    //listBox1.Invalidate();       
                }
            }

在下面的实现中，当从数据库中删除部门时，列表框会刷新当前集合

private void button1_Click(object sender, EventArgs e)
    {
        try {
            using (var uow = new UnitOfWork(new SellContext()))
            {
                int count = uow.Departments.FindDepartmentByName(txtDeptName.Text.ToString());
                if (count>0)
                {
                    MessageBox.Show("This Department Already Exists", "SellRight", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                }

                else
                {
                    department dept = new department();
                    dept.DepartmentName = txtDeptName.Text.ToString();
                    uow.Departments.Create(dept);
                    if (uow.Complete() > 0)
                    {           
                        MessageBox.Show("New Department Created", "SellRight", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        txtDeptName.Text = "";
                        ShowData();      
                    }
                    else
                    {
                        MessageBox.Show("Unable to add Department", "SellRight", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        txtDeptName.Text = "";
                        ShowData();
                    }
                }
            }                              
        }
        catch(Exception ex)
        {
            ex.ToString();
        }
    }

Answer 6

也许此解决方案没有更好的性能，但是经过多次尝试和几个小时，它才对我有用：

此行是在表单构造函数上执行的：

listBox1.DataSource = myData;

This lines were executed after the information was modified:
listBox1.DataSource = new List<Movil>();
listBox1.DataSource = myData;

希望有帮助！

Answer 7

刷新也可以通过

进行

listbox.ItemsSource = null;
listbox.ItemsSource = data;

如何刷新ListBox的DataSource

7 个答案: