ASP.NET Razor - VB Variables
Variables are named entities used to store data.
Variables
Variables are used to store data.
A variable name must begin with an alphabetic character and cannot contain spaces or reserved characters.
A variable can be of a specified type, indicating the type of data it stores. A string variable stores string values ("Welcome to example.com"), an integer variable stores numeric values (103), a date variable stores date values, and so on.
Variables are declared using the Dim keyword, or by specifying a type (if you want to declare a type), but ASP.NET can usually automatically determine the data type.
Examples
Dim greeting = "Welcome to example.com"
Dim counter = 103
Dim today = DateTime.Today
// Using data types:
Dim greeting As String = "Welcome to example.com"
Dim counter As Integer = 103
Dim today As DateTime = DateTime.Today
Data Types
The following lists commonly used data types:
| Type | Description | Example |
|---|---|---|
| integer | Integer (whole numbers) | 103, 12, 5168 |
| double | 64-bit floating point number | 3.14, 3.4e38 |
| decimal | Decimal number (high precision) | 1037.196543 |
| boolean | Boolean | true, false |
| string | String | "Hello example.com", "John" |
Operators
Operators tell ASP.NET what kind of commands to perform in expressions.
The VB language supports multiple operators. The following lists commonly used operators:
| Operator | Description | Example |
|---|---|---|
| = | Assigns a value to a variable. | i=6 |
| + - * / |
Adds a value or a variable. Subtracts a value or a variable. Multiplies by a value or a variable. Divides by a value or a variable. |
i=5+5 i=5-5 i=5*5 i=5/5 |
| += -= |
Increments the variable. Decrements the 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 <>10 |
| < > <= >= |
Less than. Greater than. Less than or equal to. Greater than or equal to. |
if i<10 if i>10 if i<=10 if i>=10 |
| & | Concatenates strings (a series of interrelated things). | "w3" & "schools" |
| . | Dot. Separates objects and methods. | DateTime.Hour |
| () | Parentheses. Groups values. | (i+5) |
| () | Parentheses. Passes parameters. | x=Add(i,5) |
| () | Parentheses. Accesses values in arrays or collections. | name(3) |
| Not | Not. Reverses true/false. | if Not ready |
| And OR |
Logical AND. Logical OR. |
if ready And clear if ready Or clear |
| AndAlso orElse |
Extended logical AND. Extended logical OR. |
if ready AndAlso clear if ready OrElse clear |
Converting Data Types
Converting from one data type to another is sometimes useful.
The most common example is converting string input to another type, such as an integer or a date.
As a general rule, user input is treated as strings, even if the user enters numbers. Therefore, numeric input must be converted to numbers before it can be used in calculations.
The following lists commonly used conversion methods:
| Method | Description | Example |
|---|---|---|
| AsInt() IsInt() |
Converts a string to an integer. | if myString.IsInt() then myInt=myString.AsInt() end if |
| AsFloat() IsFloat() |
Converts a string to a floating-point number. | if myString.IsFloat() then myFloat=myString.AsFloat() end if |
| AsDecimal() IsDecimal() |
Converts a string to a decimal number. | if myString.IsDecimal() then myDec=myString.AsDecimal() end if |
| AsDateTime() IsDateTime() |
Converts a string to the ASP.NET DateTime type. | myString="10/10/2012" myDate=myString.AsDateTime() |
| AsBool() IsBool() |
Converts a string to a boolean. | myString="True" myBool=myString.AsBool() |
| ToString() | Converts any data type to a string. | myInt=1234 myString=myInt.ToString() |
Other Extensions