Статья
11/18/2011

Interaction.Switch Method

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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)

Syntax

'Declaration
Public Shared Function Switch ( _
    ParamArray VarExpr As Object() _
) As Object

public static Object Switch(
    params Object[] VarExpr
)

Parameters

VarExpr
Type: array<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.

Remarks

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.

Note:
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.

Examples

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

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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