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Variables and Data Types

Explore how to create and use variables, including naming rules, assignment, and initialization in C#. Understand primitive types, type inference with var, and work with arrays. This lesson helps you grasp C# fundamentals essential for writing reliable and readable code using .NET's type system.

Applications need to store and process information. Variables provide a way to do this.

Variables

Variables are used to store data within a program. They represent a named area of computer memory that holds a value of a particular type. The type determines what kind of information a variable can store.

The basic syntax for declaring a variable is as follows:

variable_type variable_name;

Valid variable names must meet the following requirements:

  • The name can contain an underscore and any number and letter, while the first character in the name must be a letter or underscore.

  • The name can’t contain punctuation marks or spaces.

  • We can’t use a C# keyword as a variable name (unless we prefix it with @, though this is rare).

Although we can give any name to our C# variables, it’s highly recommended to use descriptive names. For instance, if we want to store a person’s first name, we can declare a variable as follows:

string name;

In the example above, we create a variable called name that has the string type. The string type represents text.

Case sensitivity

C# is case-sensitive. This means that depending on the character case, the same names can represent different classes, methods, and variables.

For instance, in the following code, we have a string variable named name. We can create another string variable just below and name it Name.

string name;
string Name;
...
name = "John";

We can combine declaration and ...