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Interaction.Switch(Object[]) Method

Definition

Namespace:
Microsoft.VisualBasic
Assembly:
Microsoft.VisualBasic.Core.dll
Assembly:
Microsoft.VisualBasic.dll
Source:
Interaction.vb
Source:
Interaction.vb
Source:
Interaction.vb
Source:
Interaction.vb

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

public:
 static System::Object ^ Switch(... cli::array <System::Object ^> ^ VarExpr);
public static object? Switch(params object?[]? VarExpr);
public static object Switch(params object[] VarExpr);
static member Switch : obj[] -> obj
Public Function Switch (ParamArray VarExpr As Object()) As Object

Parameters

VarExpr
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.

Returns

Object

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

Exceptions

ArgumentException

Number of arguments is odd.

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

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.

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.

Applies to

See also