In VB.NET, a variable is used to hold the value that can be used further in the programming.
The Visual Basic compiler uses the Dim statement to determine the variable's data type and other information, such as what code can access the variable.
In VB.NET, the declaration of a variable involves giving the variable a name and defining the data type to which it belongs. We use the following syntax:
Dim VarName as DataType
In the above syntax, VarName is the variable name while DataType is the name to which the variable belongs.
The following example declares a variable to hold an Integer value.
Dim numberOfCustomers As Integer
In the above example, numberOfCustomers is the variable name while Integer is the data type to which variable numberOfCustomers belongs.
You can specify any data type or the name of an enumeration, structure, class, or interface.
Dim finished As Boolean
Dim monitorBox As System.Windows.Forms.Form
For a reference type, you use the New keyword to create a new instance of the class or structure that is specified by the data type.
Dim bottomLabel As New System.Windows.Forms.Label
If you use New, you do not use an initializer expression. Instead, you supply arguments, if they are required, to the constructor of the class from which you are creating the variable.
You can assign a value to a variable when it is created. For a value type, you use an initializer to supply an expression to be assigned to the variable. The expression must evaluate to a constant that can be calculated at compile time.
Dim quantity As Integer = 10
Dim message As String = "Just started"
If an initializer is specified and a data type is not specified in an As clause, type inference is used to infer the data type from the initializer.
' Use explicit typing.
Dim num1 As Integer = 3
' Use local type inference.
Dim num2 = 3
In the above example, both num1 and num2 are strongly typed as integers. In the second declaration, type inference infers the type from the value 3.
You can use an object initializer to declare instances of named and anonymous types. The following code creates an instance of a Student class and uses an object initializer to initialize properties.
Dim author As New Author With {.First = "Michael",
.Last = "Tucker"}
You can declare several variables in one declaration statement, specifying the variable name for each one, and following each array name with parentheses. Multiple variables are separated by commas.
Dim num1, num2, numbers() As Integer
If you declare more than one variable with one As clause, you cannot supply an initializer for that group of variables.
You can specify different data types for different variables by using a separate As clause for each variable you declare. Each variable takes the data type specified in the first As clause encountered after its variable name part.
Dim a, b, c As Single, x, y As Double, i As Integer