C# 中的枚举和组合框

发布于 2024-10-19 06:45:34 字数 793 浏览 2 评论 0原文

我目前正在开发一个 C# 应用程序。

我需要使用带有组合框的枚举来获取选定的月份。我有以下内容来创建枚举：

enum Months 
{ 
   January = 1,
   February,
   March,
   April,
   May,
   June,
   July,
   August,
   September,
   October,
   November,
   December 
};

然后，我使用以下内容初始化组合框：

cboMonthFrom.Items.AddRange(Enum.GetNames(typeof(Months)));

这段代码工作正常，但问题是当我尝试获取所选月份的所选枚举值时。

为了从 ComboBox 中获取枚举值，我使用了以下方法：

private void cboMonthFrom_SelectedIndexChanged(object sender, EventArgs) 
{
   Months selectedMonth = (Months)cboMonthFrom.SelectedItem;
   Console.WriteLine("Selected Month: " + (int)selectedMonth);
}

但是，当我尝试运行上面的代码时，它会出现错误：发生了“System.InvalidCastException”类型的第一次机会异常 。

我做错了什么。

感谢您提供的任何帮助

原文

I am currently developing a C# application.

I need to use an Enum with a ComboBox to get the selected month. I have the following to create the Enum:

enum Months 
{ 
   January = 1,
   February,
   March,
   April,
   May,
   June,
   July,
   August,
   September,
   October,
   November,
   December 
};

I then initialise the ComboBox using the following:

cboMonthFrom.Items.AddRange(Enum.GetNames(typeof(Months)));

This bit of code works fine however the problem is when I try to get the selected Enum value for the selected month.

To get the Enum value from the ComboBox I have used the following:

private void cboMonthFrom_SelectedIndexChanged(object sender, EventArgs) 
{
   Months selectedMonth = (Months)cboMonthFrom.SelectedItem;
   Console.WriteLine("Selected Month: " + (int)selectedMonth);
}

However, when I try to run the code above it comes up with an error saying A first chance exception of type 'System.InvalidCastException' occurred.

What I have done wrong.

Thanks for any help you can provide

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残龙傲雪 2024-10-26 06:45:34

尝试这个

Months selectedMonth = (Months)Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem.ToString());

而不是

Months selectedMonth = (Months)cboMonthFrom.SelectedItem;

用正确的更改更新

Try this

Months selectedMonth = (Months)Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem.ToString());

instead of

Months selectedMonth = (Months)cboMonthFrom.SelectedItem;

Updated with correct changes

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灯下孤影 2024-10-26 06:45:34

问题是您使用字符串名称填充组合框（Enum.GetNames 返回string[]），然后尝试将其转换为枚举。一种可能的解决方案可能是：

Months selectedMonth = (Months)Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem);

我还会考虑使用 .Net 中的现有月份信息，而不是添加枚举：

var formatInfo = new System.Globalization.DateTimeFormatInfo();

var months = Enumerable.Range(1, 12).Select(n => formatInfo.MonthNames[n]);

The issue is that you're populating combobox with string names (Enum.GetNames returns string[]) and later you try to cast it to your enum. One possible solution could be:

Months selectedMonth = (Months)Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem);

I would also consider using existing month information from .Net instead of adding your enum:

var formatInfo = new System.Globalization.DateTimeFormatInfo();

var months = Enumerable.Range(1, 12).Select(n => formatInfo.MonthNames[n]);

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蓝颜夕 2024-10-26 06:45:34

尝试

Months selectedMonth = 
    (Months) Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem);

Try

Months selectedMonth = 
    (Months) Enum.Parse(typeof(Months), cboMonthFrom.SelectedItem);

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哆兒滾 2024-10-26 06:45:34

确实没有理由使用Enum.GetNames。如果您确实想要月份，为什么要将字符串存储在 ComboBox 中？

只需使用 Enum.GetValues 即可：

foreach (var month in Enum.GetValues(typeof(Months)))
    cboMonthFrom.Items.Add(month);

[...]

// This works now
Months selectedMonth = (Months)cboMonthFrom.SelectedItem;

There is really no reason to use Enum.GetNames at all. Why store strings in the ComboBox if you actually want the months?

Just use Enum.GetValues instead:

foreach (var month in Enum.GetValues(typeof(Months)))
    cboMonthFrom.Items.Add(month);

[...]

// This works now
Months selectedMonth = (Months)cboMonthFrom.SelectedItem;

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