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Interaction.Switch Method

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
)
public static Object Switch (
	Object[] VarExpr
)
public static function Switch (
	... VarExpr : Object[]
) : Object
Not applicable.

Parameters

VarExpr

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

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

For more detailed information, see the Visual Basic topic Switch Function.

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.

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.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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