Knowledge Base

You receive a "Data Type Mismatch" error message when you set the ControlSource property of a combo box or a list box to a Date field type in Visual FoxPro

Article ID: 156550

Article Last Modified on 2/12/2007

Microsoft Visual FoxPro 3.0 Standard Edition
Microsoft Visual FoxPro 3.0b Standard Edition
Microsoft Visual FoxPro 5.0 Standard Edition
Microsoft Visual FoxPro 6.0 Professional Edition
Microsoft Visual FoxPro 7.0 Professional Edition
Microsoft Visual FoxPro 8.0 Professional Edition
Microsoft Visual FoxPro 9.0 Professional Edition

This article was previously published under Q156550

SYMPTOMS

In Microsoft Visual FoxPro, if you set the ControlSource property of a combo box or a list box to a Date field type, you receive the following error message 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 message when the form runs.

WORKAROUND

To work around this problem, use 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 box or the list box. The DTOC() function changes the data type from Date to Character. For example, to fix the example that is described in the "Steps to reproduce the behavior" section, 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 the list box, use a REPLACE statement, instead of the ControlSource property, to put 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 the behavior

Create a form. Name the form test.
Put 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 located in the \\Program Files\Microsoft Visual Studio\Common\Samples\Data folder.

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. You receive an error message.

Additional query words: kbdsd VFoxWin

Keywords: KB156550