Why is C# statically typed?

Question

I am a PHP web programmer who is trying to learn C#.

I would like to know why C# requires me to specify the data type when creating a variable.

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Answer 1

Ultimately because Anders Hejlsberg said so...

Answer 2

One things that hasn't been mentioned is that C# is a CLS (Common Language Specification) compliant language. This is a set of rules that a .NET language has to adhere to in order to be interopable with other .NET languages.

So really C# is just keeping to these rules. To quote this MSDN article:

The CLS helps enhance and ensure language interoperability by defining a set of features that developers can rely on to be available in a wide variety of languages. The CLS also establishes requirements for CLS compliance; these help you determine whether your managed code conforms to the CLS and to what extent a given tool supports the development of managed code that uses CLS features.

If your component uses only CLS features in the API that it exposes to other code (including derived classes), the component is guaranteed to be accessible from any programming language that supports the CLS. Components that adhere to the CLS rules and use only the features included in the CLS are said to be CLS-compliant components

Part of the CLS is the CTS the Common Type System.

If that's not enough acronyms for you then there's a tonne more in .NET such as CLI, ILasm/MSIL, CLR, BCL, FCL,

Answer 3

C# is a statically-typed, strongly-typed language like C or C++. In these languages all variables must be declared to be of a specific type.

Answer 4

C#, as others have pointed out, is a strongly, statically-typed language.

By stating up front what the type you're intending to create is, you'll receive compile-time warnings when you try to assign an illegal value. By stating up front what type of parameters you accept in methods, you receive those same compile-time warnings when you accidentally pass nonsense into a method that isn't expecting it. It removes the overhead of some paranoia on your behalf.

Finally, and rather nicely, C# (and many other languages) doesn't have the same ridiculous, "convert anything to anything, even when it doesn't make sense" mentality that PHP does, which quite frankly can trip you up more times than it helps.

Answer 5

Static typing also allows the compiler to make better optimizations, and skip certain steps. Take overloading for example, where you have multiple methods or operators with the same name differing only by their arguments. With a dynamic language, the runtime would need to grade each version in order to determine which is the best match. With a static language like this, the final code simply points directly to the appropriate overload.

Static typing also aids in code maintenance and refactoring. My favorite example being the Rename feature of many higher-end IDEs. Thanks to static typing, the IDE can find with certainty every occurrence of the identifier in your code, and leave unrelated identifiers with the same name intact.

I didn't notice if it were mentioned yet or not, but C# 4.0 introduces dynamic checking VIA the dynamic keyword. Though I'm sure you'd want to avoid it when it's not necessary.

Answer 6

In C# 3.0, you can use the 'var' keyword - this uses static type inference to work out what the type of the variable is at compile time

var foo = new ClassName();

variable 'foo' will be of type 'ClassName' from then on.