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C# Academy · Lesson

The Convert Class and Parsing

Parse and convert with Convert and TryParse.

Lesson 4 of 413 steps

The Convert Class and Parsing is a free C# Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, and your progress syncs across the web and the CoddyKit app. The C# Academy course includes 4 lessons in total.

Converting Strings to Numbers

User input arrives as text. To compute with it you must convert strings to numbers. C# offers Convert, Parse, and TryParse.

using System;

class Program
{
    static void Main()
    {
        string input = "42";
        int number = int.Parse(input);
        Console.WriteLine(number + 8);
    }
}

int.Parse

int.Parse turns a numeric string into an int. It throws a FormatException if the text is not a valid number.

using System;

class Program
{
    static void Main()
    {
        try
        {
            int n = int.Parse("abc");
            Console.WriteLine(n);
        }
        catch (FormatException)
        {
            Console.WriteLine("Not a valid number");
        }
    }
}

int.TryParse

int.TryParse avoids exceptions: it returns true on success and puts the result in an out parameter, or returns false on failure.

using System;

class Program
{
    static void Main()
    {
        if (int.TryParse("123", out int n))
            Console.WriteLine("Parsed: " + n);
        else
            Console.WriteLine("Failed");
    }
}

TryParse for Safe Input

TryParse is the preferred way to handle untrusted input because invalid text is handled gracefully instead of crashing.

using System;

class Program
{
    static void Main()
    {
        string[] inputs = { "10", "oops", "30" };
        int total = 0;
        foreach (var s in inputs)
        {
            if (int.TryParse(s, out int v))
                total += v;
        }
        Console.WriteLine("Total of valid: " + total);
    }
}

The Convert Class

The Convert class converts between many base types: Convert.ToInt32, Convert.ToDouble, Convert.ToBoolean, and more.

using System;

class Program
{
    static void Main()
    {
        int i = Convert.ToInt32("256");
        double d = Convert.ToDouble("3.14");
        bool b = Convert.ToBoolean("true");
        Console.WriteLine(i + ", " + d + ", " + b);
    }
}

Convert Handles null

Unlike int.Parse, Convert.ToInt32(null) returns 0 instead of throwing, which can be convenient or surprising.

using System;

class Program
{
    static void Main()
    {
        string s = null;
        int n = Convert.ToInt32(s);   // returns 0
        Console.WriteLine("Result: " + n);
    }
}

Convert Between Numeric Types

Convert also turns one numeric type into another and rounds (not truncates) when converting floating values to integers.

using System;

class Program
{
    static void Main()
    {
        double d = 7.6;
        int cast = (int)d;             // truncates -> 7
        int converted = Convert.ToInt32(d);   // rounds -> 8
        Console.WriteLine("cast=" + cast + ", convert=" + converted);
    }
}

Parsing Other Types

Most built-in types have their own Parse/TryParse: double.TryParse, bool.TryParse, DateTime.TryParse, and so on.

using System;

class Program
{
    static void Main()
    {
        bool okD = double.TryParse("2.5", out double d);
        bool okB = bool.TryParse("True", out bool flag);
        Console.WriteLine(okD + ":" + d + ", " + okB + ":" + flag);
    }
}

ToString for the Reverse

To go from a number back to text, call ToString(), optionally with a format string.

using System;

class Program
{
    static void Main()
    {
        int n = 255;
        double price = 12.5;
        Console.WriteLine(n.ToString());
        Console.WriteLine(price.ToString("C"));   // currency format
    }
}

Choosing the Right Tool

Use TryParse for user input you cannot trust, Parse when input is guaranteed valid, and Convert when handling nulls or converting between many types.

using System;

class Program
{
    static void Main()
    {
        string userInput = "55x";
        int value = int.TryParse(userInput, out int v) ? v : -1;
        Console.WriteLine(value == -1 ? "Invalid input" : "Got " + value);
    }
}

Putting It Together

A robust input flow validates with TryParse, defaults on failure, then computes safely.

using System;

class Program
{
    static int ReadAge(string input)
    {
        if (int.TryParse(input, out int age) && age >= 0)
            return age;
        return 0;   // safe default
    }

    static void Main()
    {
        Console.WriteLine("Age: " + ReadAge("28"));
        Console.WriteLine("Age: " + ReadAge("bad"));
    }
}

Quick Check

Test your understanding of parsing and conversion.

Answer it in the interactive lesson

Recap

Convert text to numbers with int.Parse (throws on bad input), int.TryParse (safe, returns a bool + out value), or the Convert class (handles null, rounds floats, converts many types). Prefer TryParse for untrusted input and ToString() for the reverse direction.

using System;

class Program
{
    static void Main()
    {
        if (int.TryParse("99", out int n))
            Console.WriteLine("Value: " + n);
        Console.WriteLine("Convert: " + Convert.ToInt32("7"));
    }
}
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Frequently Asked Questions

Is the “The Convert Class and Parsing” lesson free?

Yes — the full text of “The Convert Class and Parsing” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO. The C# Academy course includes 4 lessons in total.

What will I learn in “The Convert Class and Parsing”?

Parse and convert with Convert and TryParse. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C# Academy?

No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.

How long does the “The Convert Class and Parsing” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C# Academy lesson?

Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Value Types vs Reference Types
  2. Boxing and Unboxing
  3. Implicit and Explicit Conversions
  4. The Convert Class and Parsing
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