Interaction.Switch Method
Evaluates a list of expressions and returns an Object value corresponding to the first expression in the list that is True.
Assembly: Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)
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.ObjectEvaluates 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.
 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. |
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 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
