Convert.ToBoolean 失败并显示“0"价值 [英] Convert.ToBoolean fails with "0" value

问题描述

我正在尝试将值 "0" ( System.String ) 转换为它的 Boolean 表示，例如:

I'm trying to convert the value "0" ( System.String ) to its Boolean representation, like:

var myValue = Convert.ToBoolean("0"); // throwing an exception here

我查看了 MSDN 页面，在代码示例块中，我找到了这些行:

I've looked at the MSDN page, and in the code-sample block, I found these lines:

ConvertToBoolean("0");
// ...
Unable to convert '0' to a Boolean.

在我的代码中，我像这样从 System.String 转换为 Boolean:

In my code, I'm converting from the System.String to Boolean like this:

// will be OK, but ugly code
var myValue = Convert.ToBoolean(Convert.ToInt32("0"));

• 有没有其他方法可以转换为 Boolean 类型而不用这么难看的代码?
• 为什么会出现这样的异常?因为从引用类型System.String转换为值类型System.Boolean，但是System.Int32也是值类型，不是吗?
• Is there any other way to convert to the Boolean type with not such ugly code?
• Why does such an exception occur? Because of converting from the reference type System.String to the value type the System.Boolean, but System.Int32 is also a value type, isn't it?

推荐答案

发生这种情况是因为 Convert.ToBoolean 期待以下之一:

This is happening because Convert.ToBoolean is expecting one of the following:

• "True"(字符串)= true
• "False"(字符串)= false
• 0(数字类型；int、double、float 等)= false
• 任何非0(数字类型；...)= true
• null = false
• "True" (String) = true
• "False" (String) = false
• 0 (numerical type; int, double, float, etc.) = false
• Any non-0 (numerical type; ...) = true
• null = false

任何other值对于Boolean都是无效的.

Any other value is invalid for Boolean.

您已经有了一个干净的方法:

var myValue = Convert.ToBoolean(Convert.ToInt32("0"));

<小时>

您可以创建一个扩展方法来处理其中一些情况，同时隐藏处理转换的丑陋之处.

---

You can create an extension method that will handle a few of these cases for you, while hiding away the ugliness of handling the conversion.

这个扩展提供了对Boolean的非常松散的解释:

This extension provides a very loose interpretation of Boolean:

• "True" (String) = true
• "False" (String) = false
• "0" (String) = false
• 任何其他字符串 = true
• "True" (String) = true
• "False" (String) = false
• "0" (String) = false
• Any other string = true

代码:

public static class Extensions
{
    public static Boolean ToBoolean(this string str)
    {
        String cleanValue = (str ?? "").Trim();
        if (String.Equals(cleanValue, "False", StringComparison.OrdinalIgnoreCase))
            return false;
        return
            (String.Equals(cleanValue, "True", StringComparison.OrdinalIgnoreCase)) ||
            (cleanValue != "0");
    }
}

<小时>

或者，如果您想要更严格的方法，遵循 .NET Framework 的要求；然后只需使用 try/catch 语句:

public static class Extensions
{
    public static Boolean ToBoolean(this string str)
    {
        try
        {
            return Convert.ToBoolean(str);
        }
        catch { }
        try
        {
            return Convert.ToBoolean(Convert.ToInt32(str));
        }
        catch { }
        return false;
    }
}

尽管不是 clean 或 pretty 方法，但它保证了获得正确值的更多可能性.而且，Extensions 类隐藏在您的数据/业务代码之外.

Albeit, not a clean or pretty approach, but it guarantees more possibilities of getting the correct value. And, the Extensions class is tucked away from your data/business code.

最后，你的转换代码使用起来比较简单:

In the end, your conversion code is relatively simple to use:

String myString = "1";
Boolean myBoolean = myString.ToBoolean();

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