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

 Last reviewed: January 10, 1997
Article ID: Q156550
The information in this article applies to:
  • Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0

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

  1. Create a form called test.
2. 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.
3. 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.

    • KBCategory: kbprg kbprb
    KBSubcategory: FxprgGeneral
    Additional reference words: 3.00 3.00b 5.00 kbdsd VFoxWin



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    Last reviewed: January 10, 1997
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