C# Convert.ToInt32 Method

The Convert.ToInt32 method in C# is used to convert various data types to a 32-bit signed integer. It is commonly used to convert strings, floating-point numbers, and other numeric types to integers, providing a versatile approach to type conversion.

Syntax

Following are the most common syntax forms for Convert.ToInt32 −

Convert.ToInt32(value);
Convert.ToInt32(value, fromBase);

Parameters

• value − The value to convert (string, double, decimal, bool, etc.)
• fromBase − Optional. The base of the number system (2, 8, 10, or 16)

Return Value

Returns a 32-bit signed integer equivalent to the specified value. Throws FormatException if the string cannot be converted, or OverflowException if the value is outside the range of a 32-bit integer.

Converting String to Integer

The most common use case is converting string representations of numbers to integers −

using System;

class Program {
   static void Main() {
      string str = "12";
      Console.WriteLine("String: " + str);
      int n = Convert.ToInt32(str);
      Console.WriteLine("Number: " + n);
      Console.WriteLine("Type: " + n.GetType());
   }
}

The output of the above code is −

String: 12
Number: 12
Type: System.Int32

Converting Different Data Types

The Convert.ToInt32 method can handle various data types including floating-point numbers, booleans, and characters −

using System;

class Program {
   static void Main() {
      // Converting double to int
      double dbl = 15.7;
      int fromDouble = Convert.ToInt32(dbl);
      Console.WriteLine("From double 15.7: " + fromDouble);
      
      // Converting boolean to int
      bool flag = true;
      int fromBool = Convert.ToInt32(flag);
      Console.WriteLine("From boolean true: " + fromBool);
      
      // Converting char to int
      char ch = '9';
      int fromChar = Convert.ToInt32(ch.ToString());
      Console.WriteLine("From char '9': " + fromChar);
   }
}

The output of the above code is −

From double 15.7: 16
From boolean true: 1
From char '9': 9

Using Different Number Bases

You can convert strings representing numbers in different bases (binary, octal, hexadecimal) to integers −

using System;

class Program {
   static void Main() {
      // Converting from binary (base 2)
      string binary = "1010";
      int fromBinary = Convert.ToInt32(binary, 2);
      Console.WriteLine("Binary 1010 to decimal: " + fromBinary);
      
      // Converting from hexadecimal (base 16)
      string hex = "FF";
      int fromHex = Convert.ToInt32(hex, 16);
      Console.WriteLine("Hex FF to decimal: " + fromHex);
      
      // Converting from octal (base 8)
      string octal = "77";
      int fromOctal = Convert.ToInt32(octal, 8);
      Console.WriteLine("Octal 77 to decimal: " + fromOctal);
   }
}

The output of the above code is −

Binary 1010 to decimal: 10
Hex FF to decimal: 255
Octal 77 to decimal: 63

Exception Handling

When converting strings that cannot be parsed as integers, Convert.ToInt32 throws exceptions. It's good practice to handle these exceptions −

using System;

class Program {
   static void Main() {
      string[] testValues = {"123", "abc", "999999999999999999", null};
      
      foreach (string value in testValues) {
         try {
            int result = Convert.ToInt32(value);
            Console.WriteLine($"'{value}' converted to: {result}");
         } catch (FormatException) {
            Console.WriteLine($"'{value}' - Invalid format");
         } catch (OverflowException) {
            Console.WriteLine($"'{value}' - Value too large");
         } catch (ArgumentNullException) {
            Console.WriteLine("null - Cannot convert null value");
         }
      }
   }
}

The output of the above code is −

'123' converted to: 123
'abc' - Invalid format
'999999999999999999' - Value too large
null - Cannot convert null value

Conclusion

The Convert.ToInt32 method provides a robust way to convert various data types to integers in C#. It supports multiple number bases and automatically handles rounding for floating-point numbers, but developers should implement proper exception handling for production code to manage invalid input gracefully.