PRB: Data Type Mismatch Error with Combo Box or List Box

ID: Q156550

The information in this article applies to:

Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 6.0

SYMPTOMS

Setting the ControlSource property of a combo or list box to a Date type field produces the following error at run time:

Error with <comboname>-Value: Data Type Mismatch. Unbinding object <comboname>

CAUSE

Combo boxes and list boxes handle only Character, Numeric, and Null data types. Other field types produce an error when the form runs.

WORKAROUND

You can work around by using a SELECT - SQL statement to create an array, instead of setting the ControlSource property of a combo box or list box to a Date type field. Use the array in the RowSource property of the combo or list box. The DTOC() function changes the data type from Date to Character. For instance, to fix the example illustrated in the STEPS TO REPRODUCE BEHAVIOR section below, you can use the following code in the Init method of the form:


   SELECT DTOC(order_date) FROM orders INTO ARRAY adates
   THISFORM.combo1.RowSource=THISFORM.combo1.RowSource

In the Valid event of the combo box or list box, use a REPLACE statement, instead of the ControlSource property, to place the value in the other table:


   REPLACE employee.hire_date WITH CTOD(THISFORM.combo1.Value)

The CTOD() function converts the selection back into a Date data type.

STATUS

This behavior is by design.

MORE INFORMATION

Combo box and list box objects do not handle all data types in the ControlSource property. The ControlSource property of a combo box or list box object can contain only data types of Character, Numeric, or Null.

Steps to Reproduce Behavior

Create a form called test.

Place the orders and employee tables from the Testdata database in the data environment of the form. Testdata is located in the Vfp\Samples\Data folder.

NOTE: In Visual FoxPro 6.0, Sample data is locate under \\Program Files\Microsoft Visual Studio\Common\Samples\Data

Add a combo box or list box to the form and set the following properties:


      ControlSource=employee.hire_date
      RowSource=orders.order_date
      RowSourceType=Fields

Run the form and the error appears.

Additional query words: kbdsd VFoxWin

Keywords : FxprgGeneral
Version : WINDOWS:3.0,3.0b,5.0,6.0
Platform : WINDOWS
Issue type :