_GETEXPR System Variable

_GETEXPR contains the empty string by default; the empty string indicates that the standard Visual FoxPro Expression Builder dialog box is displayed when the GETEXPR command is executed or when you invoke the Expression Builder dialog box from within Visual FoxPro.

You can create your own Expression Builder program that is executed when the GETEXPR command is executed or when you invoke the Expression Builder dialog box from within Visual FoxPro. Your Expression Builder program must contain an LPARAMETERS or PARAMETERS statement as the first executable line of the program to accept four parameters that Visual FoxPro passes to the program. The parameters are listed below in the order they are passed:

For example, the following could be the first executable line of your Expression Builder program:

LPARAMETERS cExpressionType, cErrorMessageText, ;
   cDefaultExpression, cCaptionText

If your Expression Builder program is executed when the Expression Builder dialog box is invoked from within Visual FoxPro, the first three parameters contain the empty string and the fourth parameter contains cCaptionText, the caption that appears in the Expression Builder.

Note that the Visual FoxPro Expression Builder is a modal dialog. Your Expression Builder program should set its form properties to the following values to create a modal dialog:

Reference

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