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Declare statement

  • Makale

Used at the module level to declare references to external procedures in a dynamic-link library (DLL).

Note

Declare statements with the PtrSafe keyword is the recommended syntax. Declare statements that include PtrSafe work correctly in the VBA version 7 development environment on both 32-bit and 64-bit platforms only after all data types in the Declare statement (parameters and return values) that need to store 64-bit quantities are updated to use LongLong for 64-bit integrals or LongPtr for pointers and handles. To ensure backwards compatibility with VBA version 6 and earlier, use the following construct:

#If VBA7 Then 
Declare PtrSafe Sub... 
#Else 
Declare Sub... 
#EndIf

Syntax 1

[ Public | Private ] Declare Sub name Lib "libname" [ Alias "aliasname" ] [ ( [ arglist ] ) ]

Syntax 2

[ Public | Private ] Declare Function name Lib "libname" [ Alias "aliasname" ] [ ( [ arglist ] ) ] [ As type ]

VBA7 Declare statement syntax

Note

For code to run in 64-bit versions of Microsoft Office, all Declare statements must include the PtrSafe keyword, and all data types in the Declare statement (parameters and return values) that need to store 64-bit quantities must be updated to use LongLong for 64-bit integrals or LongPtr for pointers and handles.

Syntax 1 (Sub)

[ Public | Private ] Declare PtrSafe Sub name Lib "libname" [ Alias "aliasname" ] [ ( [ arglist ] ) ]

Syntax 2 (Function)

[ Public | Private ] Declare PtrSafe Function name Lib "libname" [ Alias "aliasname" ] [ ( [ arglist ] ) ] [ As type ]

Part Description
Public Optional. Used to declare procedures that are available to all other procedures in all modules.
Private Optional. Used to declare procedures that are available only within the module where the declaration is made.
PtrSafe Required on 64-bit. The PtrSafe keyword asserts that a Declare statement is safe to run in 64-bit versions of Microsoft Office.
Sub Optional (either Sub or Function must appear). Indicates that the procedure doesn't return a value.
Function Optional (either Sub or Function must appear). Indicates that the procedure returns a value that can be used in an expression.
name Required. Any valid procedure name. Note that DLL entry points are case-sensitive.
Lib Required. Indicates that a DLL or code resource contains the procedure being declared. The Lib clause is required for all declarations.
libname Required. Name of the DLL or code resource that contains the declared procedure.
Alias Optional. Indicates that the procedure being called has another name in the DLL. This is useful when the external procedure name is the same as a keyword. You can also use Alias when a DLL procedure has the same name as a public variable, constant, or any other procedure in the same scope. Alias is also useful if any characters in the DLL procedure name aren't allowed by the DLL naming convention.
aliasname Optional. Name of the procedure in the DLL or code resource. If the first character is not a number sign (#), aliasname is the name of the procedure's entry point in the DLL. If (#) is the first character, all characters that follow must indicate the ordinal number of the procedure's entry point.
arglist Optional. List of variables representing arguments that are passed to the procedure when it is called.
type Optional. Data type of the value returned by a Function procedure; may be Byte, Boolean, Integer, Long, LongLong, LongPtr, Currency, Single, Double, Decimal (not currently supported), Date, String (variable length only), Variant, a user-defined type, or an object type. (LongLong is a valid declared type only on 64-bit platforms.)

The arglist argument has the following syntax and parts:

[ Optional ] [ ByVal | ByRef ] [ ParamArray ] varname [ ( ) ] [ As type ]

Part Description
Optional Optional. Indicates that an argument is not required. If used, all subsequent arguments in arglist must also be optional and declared by using the Optional keyword. Optional can't be used for any argument if ParamArray is used.
ByVal Optional. Indicates that the argument is passed by value.
ByRef Indicates that the argument is passed by reference. ByRef is the default in VBA unlike in Visual Basic .NET.
ParamArray Optional. Used only as the last argument in arglist to indicate that the final argument is an Optional array of Variant elements. The ParamArray keyword allows you to provide an arbitrary number of arguments. The ParamArray keyword can't be used with ByVal, ByRef, or Optional.
varname Required. Name of the variable representing the argument being passed to the procedure; follows standard variable naming conventions.
( ) Required for array variables. Indicates that varname is an array.
type Optional. Data type of the argument passed to the procedure; may be Byte, Boolean, Integer, Long, LongLong, LongPtr, Currency, Single, Double, Decimal (not currently supported), Date, String (variable length only), Object, Variant, a user-defined type, or an object type. (LongLong is a valid declared type only on 64-bit platforms.)

Remarks

Declare Sub First Lib "MyLib" ()

If you include an argument list, the number and type of arguments are checked each time the procedure is called. The following example takes one Long argument:

Declare Sub First Lib "MyLib" (X As Long)

Note

  • You can't have fixed-length strings in the argument list of a Declare statement; only variable-length strings can be passed to procedures. Fixed-length strings can appear as procedure arguments, but they are converted to variable-length strings before being passed.
  • The vbNullString constant is used when calling external procedures, where the external procedure requires a string whose value is zero. This is not the same thing as a zero-length string ("").

Example

This example shows how the Declare statement is used at the module level of a standard module to declare a reference to an external procedure in a dynamic-link library (DLL). You can place the Declare statements in class modules if the Declare statements are Private.

' In Microsoft Windows (16-bit): 
Declare Sub MessageBeep Lib "User" (ByVal N As Integer) 
' Assume SomeBeep is an alias for the procedure name. 
Declare Sub MessageBeep Lib "User" Alias "SomeBeep"(ByVal N As Integer) 
' Use an ordinal in the Alias clause to call GetWinFlags. 
Declare Function GetWinFlags Lib "Kernel" Alias "#132"()As Long 
 
' In 32-bit Microsoft Windows systems, specify the library USER32.DLL, 
' rather than USER.DLL. Use conditional compilation to write 
' code that can run on either Win32 or Win16. 
#If Win32 Then 
    Declare Sub MessageBeep Lib "User32" (ByVal N As Long) 
#Else 
    Declare Sub MessageBeep Lib "User" (ByVal N As Integer) 
#End If 
 
 
' 64-bit Declare statement example: 
Declare PtrSafe Function GetActiveWindow Lib "User32" () As LongPtr 
 
' Conditional Compilation Example 
#If Vba7 Then 
     ' Code is running in  32-bit or 64-bit VBA7. 
     #If Win64 Then 
          ' Code is running in 64-bit VBA7. 
     #Else 
          ' Code is not running in 64-bit VBA7. 
     #End If 
#Else 
     ' Code is NOT running in 32-bit or 64-bit VBA7. 
#End If

See also

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