如何防止/取消 C# 中组合框的值更改? [英] How to prevent/cancel a combobox's value change in c#?

问题描述

我在表单顶部有一个组合框，可将可编辑数据加载到下方的字段中.如果用户进行了更改但未保存，并尝试从组合框中选择不同的选项，我想警告他们并给他们取消或保存的机会.

I have a combobox at the top of a form that loads editable data into fields below. If the user has made changes, but not saved, and tries to select a different option from the combobox, I want to warn them and give them a chance to cancel or save.

我需要一个带有可取消事件参数的BeforeValueChange"事件.

I am in need of a "BeforeValueChange" event with a cancelable event argument.

关于如何完成的任何建议?

Any advice on how to accomplish?

推荐答案

如果第一次输入，则保存 ComboBox 的 SelectedIndex when to box，然后在需要取消更改时恢复它的值.

Save the ComboBox's SelectedIndex when to box if first entered, and then restore it's value when you need to cancel the change.

cbx_Example.Enter += cbx_Example_Enter;
cbx_Example.SelectionChangeCommitted += cbx_Example_SelectionChangeCommitted;

...

private int prevExampleIndex = 0;
private void cbx_Example_Enter(object sender, EventArgs e)
{
    prevExampleIndex = cbx_Example.SelectedIndex;
}

private void cbx_Example_SelectionChangeCommitted(object sender, EventArgs e)
{
    // some custom flag to determine Edit mode
    if (mode == FormModes.EDIT) 
    {
        cbx_Example.SelectedIndex = prevExampleIndex;
    }
}

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