C# - Difference Between Var and Dynamic

There are many different datatypes available in C#, and you can declare a variable type for a particular datatype, such as int, string, or bool. C# is rich in data type. It includes several datatypes like Var, and Dynamic that allow you to store data of any type without regard to its exact data type. The type Var was introduced in C# 3.0 (.NET 3.5 with Visual Studio 2008) and the type Dynamic was introduced in C# 4.0 ( .NET 4.0 with Visual Studio 2010).

Var Keyword

Var keywords are introduced in C# 3.0. It is compile time variable and does not require boxing and unboxing. Since Var is a compile time feature, all type checking is done at compile time only. Once Var has been initialized, you can't change type stored in it.

Dynamic keyword

It was introduced in C# 4.0. It can store any type of value, and the type of the variable is unknown until runtime. so it will not support IntelliSense. It's not mandatory to initialise at declaration time. Dynamic types can be passed method parameters.

Difference

Let us see the difference between Var and Dynamic.

1. Type Inference

• var -The type is inferred by the compiler at compile time based on the assigned value. The compiler knows the type and enforces type safety.
  

  var number = 10; // Compiler infers type as int

• dynamic - The type is determined at runtime. The compiler treats dynamic type variables as object type, but defers type checking until the program is run.
  

  dynamic number = 10; // Type determined at runtime

2. Type Checking

• var - Type checking is performed at compile time. Any type mismatches will be caught by the compiler.
  

  var number = 10;
  number = "Hello"; // Compile-time error: cannot convert from 'string' to 'int'

• dynamic - Type checking is deferred until runtime, allowing for more flexible code but increasing the risk of runtime errors.
  

  dynamic number = 10;
  number = "Hello"; // No compile-time error, but can cause runtime errors

3. Casting

• var - No casting required, but the type is fixed after initialization.
  

  var number = 10;
  int doubled = number * 2; // No casting required
  

• dynamic - No casting required, and the type can change at runtime
  

  dynamic number = 10;
  number = number * 2; // No casting required
  number = "Now I'm a string"; // Still no casting required

4. IntelliSense

• var - Full IntelliSense support in development environments like Visual Studio because the type is known at compile time.
• dynamic - Limited IntelliSense support because the type is determined at runtime.
  

5. Errors

• var - Type errors are detected at compile time, leading to fewer runtime errors.
• dynamic - Errors are detected at runtime, which can lead to runtime exceptions if the operations are invalid.

Difference between Var and Dynamic type