C# bool.Parse, TryParse: Convert String to Bool

Parse bools with the bool.Parse method. Implement a method that handles more possible true and false values.

Bool.Parse. We can convert a string to a bool. This can be done with bool.Parse or bool.TryParse—or by using a custom method with relaxed parsing rules.True, FalseCastsBool

In the custom method, the strings TRUE and T should both evaluate to a true value. Further logic can be added—any truth value can be parsed.

An example. Consider the bool.Parse and bool.TryParse methods built into the .NET Framework. These are the easiest to use in programs—you don't need to add custom code.

Note: These methods can handle "true" and "false" and the uppercased versions of these things.

Warning: Invalid strings, such as "Perls", should be used with the bool.TryParse method to avoid exceptions being thrown.

C# program that uses bool.Parse and bool.TryParse using System; class Program { static void Main() { string value = "true"; bool b = bool.Parse(value); Console.WriteLine(b); // [1] value = "False"; b = bool.Parse(value); Console.WriteLine(b); // [2] value = "Perls"; if (bool.TryParse(value, out b)) { Console.WriteLine("Not reached"); } } } Output True False

BoolParser. This method parses a string to see if it matches an equivalent of yes. It tests for strings that should evaluate to true, and if none matches, it considers the default false.

Info: In this example, the static BoolParser class has three methods that help identify the equivalent bool value for an input string.


And: The first 2 methods, GetValue and IsFalse, call internally to IsTrue. The IsTrue method checks for true values.

Note: IsTrue determines whether the input matches True, Yes, or 1. It is wrapped in a try-catch block.

Finally: This exception handling could be useful if you call this method in your initialization code, where exceptions could be disastrous.

C# program that demonstrates bool parser using System; class Program { static void Main() { Console.WriteLine(BoolParser.GetValue("true")); // True Console.WriteLine(BoolParser.GetValue("okay")); // False Console.WriteLine(BoolParser.GetValue("T")); // True Console.WriteLine(BoolParser.GetValue("False")); // False Console.WriteLine(BoolParser.GetValue("No")); // False Console.WriteLine(BoolParser.GetValue("maybe")); // False Console.WriteLine(BoolParser.GetValue("YES")); // True Console.WriteLine(BoolParser.GetValue("TRUE ")); // True Console.WriteLine(BoolParser.GetValue("f")); // False Console.WriteLine(BoolParser.GetValue("1")); // True Console.WriteLine(BoolParser.GetValue("0")); // False Console.WriteLine(BoolParser.GetValue(bool.TrueString)); // True Console.WriteLine(BoolParser.GetValue(bool.FalseString)); // False } } /// <summary> /// Parse strings into true or false bools using relaxed parsing rules /// </summary> public static class BoolParser { /// <summary> /// Get the boolean value for this string /// </summary> public static bool GetValue(string value) { return IsTrue(value); } /// <summary> /// Determine whether the string is not True /// </summary> public static bool IsFalse(string value) { return !IsTrue(value); } /// <summary> /// Determine whether the string is equal to True /// </summary> public static bool IsTrue(string value) { try { // 1 // Avoid exceptions if (value == null) { return false; } // 2 // Remove whitespace from string value = value.Trim(); // 3 // Lowercase the string value = value.ToLower(); // 4 // Check for word true if (value == "true") { return true; } // 5 // Check for letter true if (value == "t") { return true; } // 6 // Check for one if (value == "1") { return true; } // 7 // Check for word yes if (value == "yes") { return true; } // 8 // Check for letter yes if (value == "y") { return true; } // 9 // It is false return false; } catch { return false; } } } Output True False True False False False True True False True False True False Specification: String input: true Bool result: True String input: false Bool result: False String input: t Bool result: True String input: f Bool result: False String input: yes Bool result: True String input: no Bool result: False String input: 1 Bool result: True String input: 0 Bool result: False String input: Is invalid Bool result: False

Note, usage. I needed this code when developing a configuration utility. I felt it would cause less worry for the users if the program was more accepting of slightly wrong values.

And: With this class, the utility program is less of a burden because it can accept more input styles.

Tip: No one needs to worry about uppercase or lowercase, or even whitespace. Users can be assured their input will be accepted.

Also: There is a bool.Parse method in the base class library for .NET. It has few options.

System.Boolean.Parse: Microsoft Docs

A summary. We looked at the bool.Parse and bool.TryParse methods. We saw an easy way to implement bool parsing with many input variants. Finally we implemented a custom parser.
Dot Net Perls
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