C# 检查是否选择了 ComboBox 值
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Check if a ComboBox value is selected
提问by Idanis
I'm writing a form which includes some buttons and a combo box. The "Ok" button is disabled by default, and I wish to enable it only after an actual value (not the combo box's name) is selected.
我正在编写一个表单，其中包含一些按钮和一个组合框。“确定”按钮默认禁用，我希望仅在选择实际值（不是组合框的名称）后启用它。
I know how to access the selected value, and how to check if a value has been selected - but these two can be done only after the form is close (using the"x" or using the "ok" button - which is disabled).
我知道如何访问选定的值，以及如何检查值是否已被选择——但这两个只能在表单关闭后才能完成（使用“x”或使用“确定”按钮——这是禁用的） .
Any ideas?
有任何想法吗？
Thanks.
谢谢。
采纳答案by Mitch
Perhaps like this:
也许像这样：
private void comboBox_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox.SelectedIndex > -1)
{
buttonOK.Enabled = true;
}
}
By default a combobox's selected index is -1 (the combobox's name, which you can't reselect after choosing another index), so if you check that it's not -1 then you know a value has been selected.
默认情况下，组合框的选定索引为 -1（组合框的名称，在选择另一个索引后无法重新选择），因此如果您检查它不是 -1，那么您就知道已选择了一个值。
However another alternative, and the one I use, is if I always want a value to be selected is to use the DropDownStyleproperty and set it to DropDownList. That way index 0 is selected by default and the user can only select items from the list and nothing else.
然而，另一种选择，也是我使用的，如果我总是想要选择一个值，则使用该DropDownStyle属性并将其设置为DropDownList. 这样，默认情况下选择索引 0，用户只能从列表中选择项目，而不能选择其他项目。
回答by rs.
You can use combobox selected index changed event
您可以使用组合框选择索引更改事件
Add this to your InitializeComboBox class
将此添加到您的 InitializeComboBox 类
this.ComboBox1.SelectedIndexChanged +=
new System.EventHandler(ComboBox1_SelectedIndexChanged);
then in selected index changed event you can check if combox box is selected
然后在选定的索引更改事件中，您可以检查是否选择了组合框
private void ComboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
ComboBox cbx= (ComboBox) sender;
Button1.Enabled = !string.IsNullOrEmpty(cbx.SelectedItem.ToString());
}
回答by spajce
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox1.SelectedIndex == -1)
button1.Enabled = false;
else
button1.Enabled = true;
//or
//button1.Enabled = comboBox1.SelectedIndex == -1;
}
