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();

Answer 2

If you know that it would be an int then you can convert it to int then to bool. Following will try for conversion to bool by attempting the string then attempting with number.

public bool ToBoolean(string value)
{
  var boolValue = false;
  if (bool.TryParse(value, out boolValue ))
  {
    return boolValue;
  }

  var number = 0;
  int.TryParse(value, out number))
  return Convert.ToBoolean(number);
}