VB.NET Language in a Nutshell, Second Edition

Name

CallByName Function

Class

Microsoft.VisualBasic.Interaction

Named Arguments

Yes, if Args ( ) is omitted

Syntax

CallByName(Object, ProcName, UseCallType, Args(  ))

Object (required; Object)

A reference to the object containing the procedure being called.

ProcName (required; String)

The name of the procedure to call.

UseCallType (required; CallType constant)

A constant of the type CallType indicating what type of procedure is being called. CallType constants are listed in the following table.

Constant	Value	Description
Method	1	The called procedure is a method.
Get	2	The called procedure retrieves a property value.
Let	4	The called procedure sets the value of a property.

Args (optional; any)

A ParamArray argument representing the arguments required by the procedure being called.

Return Value

Depends on the return value (if any) of the called procedure

Description

Provides a method for calling a class member by name.

Since ProcName is a string expression, rather than the literal name of a routine, it is possible to call routines dynamically at runtime using a string variable to hold the various procedure names.

Rules at a Glance

• The return type of CallByName is the return type of the called procedure.

• ProcName is not case sensitive.

• UseCallType can either be a numeric value or a constant of the CallType enumeration. In the latter case, the enumeration name must be specified along with the constant name, as in CallType.Method.

• Args ( ) must be a parameter array. A parameter ...