如果未选择组合框，则异常 [英] exception if combobox is not selected

问题描述

你好.我想知道，如果未选择组合框，该如何做例外.到目前为止，它会出现错误:对象引用未设置为对象的实例.如果可能的话，我希望它像请从列表中选择一个项目"那样出现. 或类似的东西.

Hello. I want to know, how do I make an exception if the combobox is not selected. So far, it will come out Error: Object reference not set to an instance of an objet. If possible, I want it to come out like "Please select an item from the list." or something like that.

string LabName = comboBoxLabNumber.SelectedItem.ToString();
string LabNumber = LabName;
string LabProblem = comboBoxProblem.SelectedItem.ToString();
string LabProb = LabProblem;

还是我应该使用if/else来做?有什么主意吗?

谢谢

Or should I just do it using if/else? Any idea?

Thanks

推荐答案

将SelectedIndex用于组合框.

Hi,

using SelectedIndex for combobox.

if(comboBoxLabNumber.SelectedIndex > -1)
{
  LabName = comboBoxLabNumber.SelectedItem.ToString();
}
else
{
  MessageBox.Show("Please select an item!");
}

尝试这种方式...

干杯:)

Try this way...

Cheers :)

然后处理异常，例如

Then handle the exception, for instance

try
{
    LabName = comboBoxLabNumber.SelectedItem.ToString();
}
catch (Exception e)
{
    MessageBox.Show("Please select an item from the list");
    // here take the appropriate action.
}

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