What advantages does using var have over the explicit type in C#? [duplicate]

Answer 1

The var is just a syntactic sugar. It is always known at compile time what type the variable is. There are no other advantages of using the var keyword.

Answer 2

Using var as the iterator variable for a foreach block is more type safe than explicit type names. For example

class Item {
  public string Name; 
}
foreach ( Item x in col ) {
  Console.WriteLine(x.Name);
}

This code could compile without warnings and still cause a runtime casting error. This is because the foreach loop works with both IEnumerable and IEnumerable<T>. The former returns values typed as object and the C# compiler just does the casting to Item under the hood for you. Hence it's unsafe and can lead to runtime errors because an IEnumerable can contain objects of any type.

On the other hand the following code will only do one of the following

1. Not compile because x is typed to object or another type which does not have a Name field / property
2. Compile and be guaranteed to not have a runtime cast error while enumerating.

The type of 'x' will be object in the case of IEnumerable and T in the case of IEnumerable<T>. No casting is done by the compiler.

foreach ( var x in col ) {
  Console.WriteLine(x.Name);
}

Answer 3

The point of var is to allow anonymous types, without it they would not be possible and that is the reason it exists. All other uses I consider to be lazy coding.