ASP.NET Razor - C# Variables

Variables are named entities used to store data.

Variables

Variables are used to store data.

Variable names must start with a letter character and cannot contain spaces or reserved characters.

Variables can be a specific type, indicating the data type of the data it stores. String variables store string values ("Welcome to CodeW3C.com"), integer variables store numeric values (103), date variables store date values, and so on.

Declare variables using the var keyword or type, but ASP.NET usually can automatically determine the data type.

Example

// Use var keyword:
var greeting = "Welcome to CodeW3C.com";
var counter = 103;
var today = DateTime.Today;
// Use data type:
string greeting = "Welcome to CodeW3C.com";
int counter = 103;
DateTime today = DateTime.Today;

Data type

Here is a list of common data types:

Type Description Example
int Integers 103, 12, 5168
float Floating-point numbers 3.14, 3.4e38
decimal Decimal 1037.196543
bool Logical values true, false
string String values "Hello CodeW3C.com", "Bill"

Operators

Operators inform ASP.NET which type of command to execute in an expression.

C# language supports various operators. Here are some common operators:

Operators Description Example
= Assign a value to a variable. i=6
  • +
  • -
  • *
  • /
  • Add value or variable
  • Subtract value or variable
  • Multiply value or variable
  • Divide value or variable
  • i=5+5
  • i=5-5
  • i=5*5
  • i=5/5
  • +=
  • -=
  • Increment variable
  • Decrement variable
  • i += 1
  • i -= 1
== Equal. Returns true if the values are equal. if (i==10)
!= Not equal. Returns true if the values are not equal. if (i!=10)
  • <
  • >
  • <=
  • >=
  • Less
  • Greater
  • Less than or equal to
  • Greater than or equal to
  • if (i<10)
  • if (i>10)
  • if (i<=10)
  • if (i>=10)
+ String concatenation (chaining or juxtaposition) "w3" + "school"
. Dot. Separate objects and methods. DateTime.Hour
() Parentheses. Group values. (i+5)
() Parentheses. Pass parameters. x=Add(i,5)
[] Parentheses. Access values in an array or collection. name[3]
! Not. Inverts true or false. if (!ready)
  • &&
  • ||
  • Logical AND
  • Logical OR
  • if (ready && clear)
  • if (ready || clear)

Convert Data Types

Converting one data type to another can be very useful sometimes.

Most common examples include converting string input to another type, such as an integer or a date.

As a rule, user input will be treated as a string, even if the input is a number. Therefore, numeric input values must be converted to numbers before they are used for calculations.

Below is a list of commonly used conversion methods:

Method Description Example
  • AsInt()
  • IsInt()
 Convert a string to an integer. if (myString.IsInt())
{myInt = myString.AsInt();}
  • AsFloat()
  • IsFloat()
 Convert a string to a floating-point number. if (myString.IsFloat())
{myFloat = myString.AsFloat();}
  • AsDecimal()
  • IsDecimal()
 Convert a string to a decimal number. if (myString.IsDecimal())
{myDec = myString.AsDecimal();}
  • AsDateTime()
  • IsDateTime()
 Convert a string to an ASP.NET DateTime type myString = "10/10/2012";
myDate = myString.AsDateTime();
  • AsBool()
  • IsBool()
 Convert a string to a logical value. myString = "True";
myBool = myString.AsBool();
ToString() Convert any data type to a string. myInt = 1234;
myString = myInt.ToString();