What is the difference between int and Int32 in C#?

Int32 is a type provided by .NET framework whereas int is an alias for Int32 in C# language. Both represent 32-bit signed integers and compile to identical code, making them functionally equivalent at runtime.

Syntax

Following is the syntax for declaring integers using both approaches −

Int32 variable1 = value;
int variable2 = value;

Key Differences

Type Equivalence

Both int and Int32 refer to the same underlying type. The following expression demonstrates their equivalence −

using System;

class Program {
   static void Main(string[] args) {
      bool areEqual = typeof(int) == typeof(Int32);
      bool bothEqualToSystem = typeof(int) == typeof(System.Int32);
      
      Console.WriteLine("int == Int32: " + areEqual);
      Console.WriteLine("int == System.Int32: " + bothEqualToSystem);
      Console.WriteLine("int hash code: " + typeof(int).GetHashCode());
      Console.WriteLine("Int32 hash code: " + typeof(Int32).GetHashCode());
   }
}

The output of the above code is −

int == Int32: True
int == System.Int32: True
int hash code: 54267293
Int32 hash code: 54267293

Using int Keyword

The int keyword is the preferred C# approach for declaring 32-bit integers −

using System;

class Program {
   static void Main(string[] args) {
      int number = 42;
      int maxValue = int.MaxValue;
      int minValue = int.MinValue;
      
      Console.WriteLine("Value: " + number);
      Console.WriteLine("Max int value: " + maxValue);
      Console.WriteLine("Min int value: " + minValue);
   }
}

The output of the above code is −

Value: 42
Max int value: 2147483647
Min int value: -2147483648

Using Int32 Type

The Int32 type requires the System namespace and is functionally identical to int −

using System;

class Program {
   static void Main(string[] args) {
      Int32 number = 42;
      Int32 maxValue = Int32.MaxValue;
      Int32 minValue = Int32.MinValue;
      
      Console.WriteLine("Value: " + number);
      Console.WriteLine("Max Int32 value: " + maxValue);
      Console.WriteLine("Min Int32 value: " + minValue);
   }
}

The output of the above code is −

Value: 42
Max Int32 value: 2147483647
Min Int32 value: -2147483648

Common Use Cases

Most C# developers prefer int for its simplicity and readability. Int32 might be used when working extensively with .NET Framework types or when emphasizing the specific bit-size in documentation.

Conclusion

The difference between int and Int32 in C# is purely syntactic − int is a C# keyword alias for the .NET type System.Int32. Both compile to identical code and have identical performance, with int being the preferred choice for most scenarios.