Switch Method

Interaction.Switch Method (Object[])

 

Evaluates a list of expressions and returns an Object value corresponding to the first expression in the list that is True.

Namespace:   Microsoft.VisualBasic
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

public static object Switch(
	params object[] VarExpr
)

Parameters

VarExpr
Type: System.Object[]

Required. Object parameter array. Must have an even number of elements. You can supply a list of Object variables or expressions separated by commas, or a single-dimensional array of Object elements.

Return Value

Type: System.Object

Evaluates a list of expressions and returns an Object value corresponding to the first expression in the list that is True.

Exception Condition
ArgumentException

Number of arguments is odd.

The argument supplied to VarExpr consists of paired expressions and values. The Switch function evaluates the odd-numbered expressions from lowest to highest index in VarExpr, and returns the even-numbered value associated with the first expression that evaluates to True. For example, if VarExpr(0) is True, Switch returns VarExpr(1), and if VarExpr(0) is False but VarExpr(2) is True, Switch returns VarExpr(3), and so on.

If you do not supply the VarExpr argument, Switch returns Nothing.

System_CAPS_noteNote

The expressions in the argument list can include function calls. As part of preparing the argument list for the call to Switch, the Visual Basic compiler calls every function in every expression. This means that you cannot rely on a particular function not being called if an expression earlier in the argument list is True.

The following example uses the Switch function to return the name of a language that matches the name of a city. It requires that Option Strict be Off.

Function matchLanguage(ByVal cityName As String) As String
    Return CStr(Microsoft.VisualBasic.Switch( 
        cityName = "London", "English", 
        cityName = "Rome", "Italian", 
        cityName = "Paris", "French"))
End Function

Because the System.Diagnostics namespace also contains a class called Switch, a call to the Switch function must be qualified with the Microsoft.VisualBasic namespace.

.NET Framework
Available since 1.1
Silverlight
Available since 2.0
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