c# - Convert.ToBoolean fails with "0" value

Question

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

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

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.

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"));

• 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?

Answer 1

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

• "True" (String) = true
• "False" (String) = false
• 0 (numerical type; int, double, float, etc.) = false
• Any non-0 (numerical type; ...) = true
• null = false

Any other value is invalid for Boolean.

You've already got a clean approach:

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

---

Edit: 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.

This extension provides a very loose interpretation of Boolean:

• "True" (String) = true
• "False" (String) = false
• "0" (String) = false
• Any other string = true

Code:

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");
    }
}

---

Alternatively, if you want a more strict approach, which follows what the .NET Framework expects; then simply use try/catch statements:

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;
    }
}

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.

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

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