How to convert a string into int in C#?

Converting a string to an integer in C# is a common task that can be accomplished using several methods. The most straightforward approach is using Int32.Parse() method, which converts the string representation of a number to its 32-bit signed integer equivalent.

Syntax

Following is the syntax for using Int32.Parse() method −

int result = Int32.Parse(stringValue);

Following is the syntax for using Convert.ToInt32() method −

int result = Convert.ToInt32(stringValue);

Following is the syntax for using int.TryParse() method −

bool success = int.TryParse(stringValue, out int result);

Using Int32.Parse() Method

The Int32.Parse() method is the most commonly used approach for converting strings to integers −

using System;

class Demo {
    static void Main() {
        string str = "9999";
        int n = Int32.Parse(str);
        Console.WriteLine("Original string: " + str);
        Console.WriteLine("Converted integer: " + n);
        Console.WriteLine("Type: " + n.GetType());
    }
}

The output of the above code is −

Original string: 9999
Converted integer: 9999
Type: System.Int32

Using Convert.ToInt32() Method

The Convert.ToInt32() method provides another way to convert strings to integers and handles null values gracefully −

using System;

class Program {
    static void Main() {
        string str1 = "12345";
        string str2 = null;
        
        int num1 = Convert.ToInt32(str1);
        int num2 = Convert.ToInt32(str2); // returns 0 for null
        
        Console.WriteLine("String '12345' converts to: " + num1);
        Console.WriteLine("Null string converts to: " + num2);
    }
}

The output of the above code is −

String '12345' converts to: 12345
Null string converts to: 0

Using int.TryParse() for Safe Conversion

The int.TryParse() method is the safest approach as it doesn't throw exceptions for invalid input −

using System;

class SafeConversion {
    static void Main() {
        string[] testStrings = {"123", "abc", "999999999999", "42.5"};
        
        foreach (string str in testStrings) {
            if (int.TryParse(str, out int result)) {
                Console.WriteLine($"'{str}' successfully converted to: {result}");
            } else {
                Console.WriteLine($"'{str}' could not be converted to integer");
            }
        }
    }
}

The output of the above code is −

'123' successfully converted to: 123
'abc' could not be converted to integer
'999999999999' could not be converted to integer
'42.5' could not be converted to integer

Comparison of Methods

Conclusion

Converting strings to integers in C# can be done using Int32.Parse(), Convert.ToInt32(), or int.TryParse(). Use TryParse() for safe conversion when input validity is uncertain, and Parse() when you're confident the input is valid.