Question

public class ComboboxItem { 
            public string Text { get; set; } 
            public string Value { get; set; }
            public override string ToString() { return Text; } 
        }

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            int selectedIndex = comboBox1.SelectedIndex;
            int selecteVal = (int)comboBox1.SelectedValue; 
            ComboboxItem selectedCar = (ComboboxItem)comboBox1.SelectedItem;
            MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));
        }

我正在添加它们：

ComboboxItem item = new ComboboxItem();
                    item.Text = cd.Name;
                    item.Value = cd.ID;
                    this.comboBox1.Items.Add(item);

我一直收到NullReferenceException并且不确定原因。文本似乎显示得很好。

Answer 1

试试这个：

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    ComboBox cmb = (ComboBox)sender;
    int selectedIndex = cmb.SelectedIndex;
    int selectedValue = (int)cmb.SelectedValue;

    ComboboxItem selectedCar = (ComboboxItem)cmb.SelectedItem;
    MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));        
}

Answer 2

由于您使用的是NullReferenceExeption，因此您获得了cmb.SelectedValue。 comboBox不知道自定义类ComboboxItem的价值是什么，所以要么：

ComboboxItem selectedCar = (ComboboxItem)comboBox2.SelectedItem;
int selecteVal = Convert.ToInt32(selectedCar.Value);

或者更好的是使用数据绑定，如：

ComboboxItem item1 = new ComboboxItem();
item1.Text = "test";
item1.Value = "123";

ComboboxItem item2 = new ComboboxItem();
item2.Text = "test2";
item2.Value = "456";

List<ComboboxItem> items = new List<ComboboxItem> { item1, item2 };

this.comboBox1.DisplayMember = "Text";
this.comboBox1.ValueMember = "Value";
this.comboBox1.DataSource = items;

Answer 3

我有类似的错误，我的班级是

public class ServerInfo
{
    public string Text { get; set; }
    public string Value { get; set; }
    public string PortNo { get; set; }

    public override string ToString()
    {
        return Text;
    }
}

但是我做了什么，我将我的类转换为ComboBox的SelectedItem属性。所以，我将拥有所选项目的所有类属性。

// Code above
ServerInfo emailServer = (ServerInfo)cbServerName.SelectedItem;

mailClient.ServerName = emailServer.Value;
mailClient.ServerPort = emailServer.PortNo;

我希望这有助于某人！干杯！

Answer 4

试试这个：

private void cmbLineColor_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataRowView drv = (DataRowView)cmbLineColor.SelectedItem;
        int selectedValue = (int)drv.Row.ItemArray[1];
    }

Answer 5

SelectedValue的问题不是转换为整数。这是主要问题，因此请注意以下代码段将对您有所帮助：

int selectedValue;
bool parseOK = Int32.TryParse(cmb.SelectedValue.ToString(), out selectedValue);

Answer 6

尝试一下：

int selectedIndex = comboBox1->SelectedIndex;
comboBox1->SelectedItem->ToString();
int selectedValue = (int)comboBox1->Items[selectedIndex];

Answer 7

您必须将所选项目转换为自定义类（ComboboxItem）试试这个：

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
ComboBox cmb = (ComboBox)sender;
            int selectedIndex = cmb.SelectedIndex;
            string selectedText = this.comboBox1.Text;
            string selectedValue = ((ComboboxItem)cmb.SelectedItem).Value.ToString();

ComboboxItem selectedCar = (ComboboxItem)cmb.SelectedItem;
MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));

}

获得组合框的选定值

7 个答案: