PRB: Error Occurs When Using DynamicCurrentControl Property

ID: Q135522

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0

SYMPTOMS

When setting the DynamicCurrentControl property of a column contained within a grid, you may get the error message "Expression is invalid. Use a valid expression for DynamicCurrentControl property."

CAUSE

This error message may occur if you used the Expression Builder to create your DynamicCurrentControl property expression. The DynamicCurrentControl property sets the active control of a column based on a certain condition. This is typically accomplished with an in-line if (IIF) statement. When you add an IIF statement to the DynamicCurrentControl property, Visual FoxPro assumes that an equal sign (=) resides at the beginning of the statement. If you have the Expression Builder creates your IIF statement, it adds an equal sign as the first character and thus cause the error message.

RESOLUTION

Remove the equal sign inserted by the Expression Builder, or do not use the expression builder to create your IIF statements for the DynamicCurrentControl property.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

1. Open or switch to Microsoft Visual FoxPro.

2. Open a new form and add a grid to it.

3. Add the Employee.dbf table, located in the \Samples\Data subdirectory of

   Visual FoxPro, to the data environment of the form.

4. In the form's Property window, set the grid's ColumnCount property to 1,

   and set the Bound property of Column1 to false (.F.).

5. Add a text frame to the Column (this will be Text2 as there will be a

   text frame called Text1 in the Column by default).

6. In the form's Property window, set the Value property of Text2 to Test.

7. Set the ControlSource property of Text1 to Employee.emp_id.

8. Use the Expression Builder to create the following statement for the

   DynamicCurrentControl property of Column1:

   IIF((LEFT(ALLTRIM(EMPLOYEE.EMP_ID),1) = "1"), "TEXT1", "TEXT2")

9. Close the Expression Builder. Note that it adds an equal sign (=) to the

   beginning of the statement.

10. Save and run the Form. Note that the error "Expression is invalid. Use

    a valid expression for DynamicCurrentControl property" appears.

11. Remove the equal sign added by the Expression Builder, and run the

    form. Note that if now functions as expected.

Additional reference words: 3.00 VFoxWin KBCategory: kbprg kbprb KBSubcategory: FxprgGeneral