In C#, we have different options to parse integer values. Amongst these, the Parse, TryParse and Convert options are the most common and have subtle differences in their usage.

I'll discuss each of these with a short console program.

Int32.Parse(string)

This converts the string representation of a number to its 32-bit signed integer equivalent.

• When string is null -> throws ArgumentNullException

• When string has a non-integer value -> throws FormatException

• When string represents a number less than MinValue or greater than MaxValue -> throws OverflowException

Example

namespace ConsoleApplication
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string str1 = "5555";
            string str2 = null;
            string str3 = "5555.55";
            string str4 = "51515815155151515511511515151515"; 
            int result;

            result = int.Parse(str1); //success - 5555

            result = int.Parse(str2); // ArgumentNullException    

            result = int.Parse(str3); //FormatException    

            result = int.Parse(str4); //OverflowException 
        }
    }
}

Convert.ToInt32(string)

This too converts the string representation of a number to its 32-bit signed integer equivalent. This internally calls the Int32.Parse() method.

• When string is null -> returns 0

• When string has a non-integer value -> throws FormatException

• When string represents a number less than MinValue or greater than MaxValue -> throws OverflowException

Example

using System;

namespace ConsoleApplication
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string str1 = "5555";
            string str2 = null;
            string str3 = "5555.55";
            string str4 = "51515815155151515511511515151515"; 
            int result;

            result = Convert.ToInt32(str1); //success - 5555

            result = Convert.ToInt32(str2); // 0    

            result = Convert.ToInt32(str3); //FormatException    

            result = Convert.ToInt32(str4); //OverflowException 
        }
    }
}

Int32.TryParse(string, out int)

This too converts the string representation of a number to its 32-bit signed integer equivalent.

• If the integer is parsed successfully -> returns true and sets the integer in the out parameter.

• If integer parsing is unsuccessful -> returns false and sets the integer in the out parameter to 0.

• When string is null -> out variable has 0

• When string has a non-integer value -> out variable has 0

• When string represents a number less than MinValue or greater than MaxValue -> out variable has 0

Example

using System;

namespace ConsoleApplication
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string str1 = "5555";
            string str2 = null;
            string str3 = "5555.55";
            string str4 = "51515815155151515511511515151515"; 
            int result;
            bool success;

            success = Int32.TryParse(str1, out result); //true - 5555

            success = Int32.TryParse(str2, out result); //false - 0    

            success = Int32.TryParse(str3, out result); //false - 0    

            success = Int32.TryParse(str4, out result); //false - 0 
        }
    }
}

Usually, the order of preference amongst these is ...

Int32.TryParse > Convert.ToInt32 > Int32.Parse

Hope this was useful!