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How to convert string into int in C#?

Revati S Misra 1366 11 Jun 2024

How to convert string into int in C#?

Ask by Revati S Misra

Updated 12 Jun 2024

1 Answers

Ashutosh Patel 12 Jun 2024

Convert string to int in C#

Converting a string to an integer in C# can be done in many ways depending on the specific needs of your application. Here are general ways to do this.

Using int.Parse

The int.Parse method is used to convert a string to an integer. Throw a FormatException if the string is not a valid integer.

Syntax-

string str = "123";
int number = int.Parse(str);
Console.WriteLine(number); // Output: 123

using int.TryParse

The int.TryParse method attempts to convert a string to an integer and returns a boolean indicating whether the conversion was successful or not. This method is safe because it does not throw an exception if the conversion fails.

Syntax-

string str = "123";
bool success = int.TryParse(str, out int number);
if (success)
{
   Console.WriteLine(number); // Output: 123
}
else
{
   Console.WriteLine("Conversion failed.");
}

Using Convert.ToInt32

The Convert.ToInt32 method converts the specified string position of any number to a 32-bit equivalent signed integer. It handles null values by returning 0 and throws a FormatException if the string is not a valid integer.

Syntax-

string str = "123";
int number = Convert.ToInt32(str);
Console.WriteLine(number); // Output: 123

Handling exceptions and edge cases

When using int.Parse or Convert.ToInt32, you must deal with potential exceptions to avoid runtime errors.

Syntax-

string strNum = "1234rter";
try
{
  int num = int.Parse(strNum);
  Console.WriteLine("Number is: "+ num);
}
catch (FormatException)
{
   Console.WriteLine("The string format is not a valid for integer.");
}
catch (OverflowException)
{
   Console.WriteLine("The number is too large or too small for an Int32.");
}

There is no need to handle exceptions in the case of int.tryParse because it returns the boolean value true or false.
int.parse- Direct convert the values so it throws the exceptions
Convert.int32- it handles null gracefully by returning 0, but throws an exception on invalid format.

Example-

The below example illustrate the different way to convert string into int in C#

using System;
// Define a delegate
public delegate void MyDelegate(string message);
public class Program
{
  public static void Main()
   {
       // using int.Parse method
       string strNum1 = "1234";
       int num1 = int.Parse(strNum1);
       Console.WriteLine("Number1 is: "+ num1);
       
       // using int.TryParse methos
       string strNum2 = "1234xyz";
       bool IsNumber = int.TryParse(strNum2, out int num2);
       if(IsNumber)
       {
           Console.WriteLine("Number2 is: "+ num2);
       }
       else
       {
           Console.WriteLine("Conversion failed: string format not valid for number");
       }
       
       // using try catch block to handle exception
       string strNum3 = "12345abc";
       try
       {
          int num = int.Parse(strNum3);
          Console.WriteLine("Number is: "+ num);
       }
       catch (FormatException)
       {
           Console.WriteLine("The string format is not a valid for integer.");
       }
       catch (OverflowException)
       {
           Console.WriteLine("The number is too large or too small for an Int32.");
       }
   }
}

Output-

Number1 is: 1234
Conversion failed: string format not valid for number
The string format is not a valid for integer.

Also, Read: What is Boxing and Unboxing in C#?

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