如何刷新ListBox的DataSource

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();
    }
}

在此示例中,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,但通过分配相同的列表,值不会真正更改.

您可以使用a BindingList<T>而不是您List<T>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

列表框未检测到您已更改DataSource.它只会在Datasource更改后刷新,因此DataSource首先设置为null:

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

您还可以清除项目,然后再次设置DataSource:

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